2009 flu pandemic
Encyclopedia
The 2009 flu pandemic (more commonly and informally known as swine flu) was an influenza pandemic
, and the second of the two pandemics involving H1N1 influenza virus (the first of them was the 1918 flu pandemic), albeit in a new version. First described in April 2009, the virus appeared to be a new strain of H1N1 which resulted when a previous triple reassortment
of bird, swine and human flu viruses further combined with a Eurasian pig flu virus, leading to the term "swine flu
" to be used for this pandemic. Unlike most strains of influenza, H1N1 does not disproportionately infect adults older than 60 years; this was an unusual and characteristic feature of the H1N1 pandemic
. Even in the case of previously very healthy persons, a small percentage will develop pneumonia
or acute respiratory distress syndrome
. This manifests itself as increased breathing difficulty and typically occurs 3–6 days after initial onset of flu symptoms. The pneumonia caused by flu can be either direct viral pneumonia or a secondary bacterial pneumonia. In fact, a November 2009 New England Journal of Medicine
article recommends that flu patients whose chest X-ray indicates pneumonia receive both antivirals and antibiotics. In particular, it is a warning sign if a child (and presumably an adult) seems to be getting better and then relapses with high fever, as this relapse may be bacterial pneumonia.
Initially coined an "outbreak", the stint began in the state of Veracruz
, Mexico, with evidence that there had been an ongoing epidemic for months before it was officially recognized as such. The Mexican government closed most of Mexico City
's public and private facilities in an attempt to contain the spread of the virus; however, it continued to spread globally, and clinics in some areas were overwhelmed by infected people. In June, the World Health Organization
(WHO) and the U.S. Centers for Disease Control and Prevention
(CDC) stopped counting cases and declared the outbreak a pandemic
.
Despite being informally called "swine flu", the H1N1 flu virus cannot be spread by eating pork or pork products; similar to other influenza viruses, it is typically contracted by person to person transmission through respiratory droplets. Symptoms usually last 4–6 days. Antivirals (oseltamivir
or zanamivir) were recommended for those with more severe symptoms or those in an at-risk group.
The pandemic began to taper off in November 2009, and by May 2010, the number of cases was in steep decline. On 10 August 2010, the Director-General of the World Health Organization, Margaret Chan
, announced the end of the H1N1 pandemic, and announced that the H1N1 influenza event has moved into the post-pandemic period. According to the latest WHO statistics (July 2010), the virus has killed more than 18,000 people since it appeared in April 2009, however they state that the total mortality (including deaths unconfirmed or unreported) from the H1N1 strain is "unquestionably higher". Critics claimed the WHO had exaggerated the danger, spreading "fear and confusion" rather than "immediate information". The WHO began an investigation to determine whether it had "frightened people unnecessarily". A flu followup study done in September 2010, found that "the risk of most serious complications was not elevated in adults or children." In an August 5, 2011 PLoS ONE article, researchers estimated that the 2009 H1N1 global infection rate was 11% to 21%, lower than what was previously expected. Serbia's B92
investigative reporting concluded that vaccine was not properly tested.
by the World Health Organization, while the U.S. Centers for Disease Control and Prevention refer to it as "novel influenza A (H1N1)" or "2009 H1N1 flu". In the Netherlands
, it was originally called "Pig Flu", but is now called "New Influenza A (H1N1)" by the national health institute
, although the media and general population use the name "Mexican Flu". South Korea
and Israel
briefly considered calling it the "Mexican virus". Later, the South Korean press used "SI", short for "swine influenza". Taiwan
suggested the names "H1N1 flu" or "new flu", which most local media adopted. The World Organization for Animal Health proposed the name "North American influenza". The European Commission
adopted the term "novel flu virus".
s, and may include a fever, cough (typically a "dry cough"), headache, muscle
or joint
pain, sore throat
, chills
, fatigue, and runny nose
. Diarrhea
, vomiting, and neurological
problems have also been reported in some cases. People at higher risk of serious complications include those aged over 65, children younger than 5, children with neurodevelopmental conditions, pregnant women (especially during the third trimester), and those of any age with underlying medical conditions, such as asthma, diabetes, obesity, heart disease, or a weakened immune system (e.g., taking immunosuppressive medications or infected with HIV). More than 70% of hospitalizations in the U.S. have been people with such underlying conditions, according to the CDC.
In September 2009, the CDC reported that the H1N1 flu "seems to be taking a heavier toll among chronically ill children than the seasonal flu usually does." Through 8 August 2009, the CDC had received 36 reports of paediatric deaths with associated influenza symptoms and laboratory-confirmed pandemic H1N1 from state and local health authorities within the United States, with 22 of these children having neurodevelopmental conditions such as cerebral palsy
, muscular dystrophy
, or developmental delays. "Children with nerve and muscle problems may be at especially high risk for complications because they cannot cough hard enough to clear their airways". From 26 April 2009, to 13 February 2010, the CDC had received reports of the deaths of 277 children with laboratory-confirmed 2009 influenza A (H1N1) within the United States.
reports that the clinical picture in severe cases is strikingly different from the disease pattern seen during epidemics of seasonal influenza. While people with certain underlying medical conditions are known to be at increased risk, many severe cases occur in previously healthy people. In severe cases, patients generally begin to deteriorate around three to five days after symptom onset. Deterioration is rapid, with many patients progressing to respiratory failure within 24 hours, requiring immediate admission to an intensive care unit. Upon admission, most patients need immediate respiratory support with mechanical ventilation
.
A November 2009 CDC recommendation stated that the following constitute "emergency warning signs" and advised seeking immediate care if a person experiences any one of these signs:
In adults:
In children:
Research later indicated that the severe flu effects in healthy young and middle-aged adults are caused by an excessive immune response.
and respiratory disease
as the strongest risk factors. Pulmonary complications are common. Primary influenza pneumonia
occurs most commonly in adults and may progress rapidly to acute lung injury requiring mechanical ventilation
. Secondary bacterial infection is more common in children. Staphylococcus aureus
, including methicillin-resistant strains, is an important cause of secondary bacterial pneumonia with a high mortality rate. Neuromuscular and cardiac complications are unusual but may occur.
A United Kingdom investigation of risk factors for hospitalisation and poor outcome with pandemic A/H1N1 influenza looked at 631 patients from 55 hospitals admitted with confirmed infection from May through September 2009. 13% were admitted to a high dependency or intensive care unit and 5% died; 36% were aged <16 years and 5% were aged ≥65 years. Non-white and pregnant patients were over-represented. 45% of patients had at least one underlying condition, mainly asthma
, and 13% received antiviral drugs before admission. Of 349 with documented chest x-rays on admission, 29% had evidence of pneumonia
, but bacterial co-infection was uncommon. Multivariate analyses showed that physician-recorded obesity on admission and pulmonary conditions other than asthma or chronic obstructive pulmonary disease
(COPD) were associated with a severe outcome, as were radiologically confirmed pneumonia and a raised C-reactive protein
(CRP) level (≥. 59% of all in-hospital deaths occurred in previously healthy people.
Fulminant
(sudden-onset) myocarditis
has been linked to infection with H1N1, with at least four cases of myocarditis confirmed in patients also infected with A/H1N1. Three out of the four cases of H1N1-associated myocarditis were classified as fulminant, and one of the patients died.
Also, there appears to be a link between severe A/H1N1 influenza infection and pulmonary embolism
. In one report, five out of 14 patients admitted to the intensive care unit with severe A/H1N1 infection were found to have pulmonary emboli.
An article published in JAMA
in September 2010 challenged previous reports and stated that children infected in the 2009 flu pandemic were no more likely to be hospitalised with complications or get pneumonia than those who catch seasonal strains. Researchers found that about 1.5% of children with the H1N1 swine flu strain were hospitalised within 30 days, compared with 3.7% of those sick with a seasonal strain of H1N1 and 3.1% with an H3N2 virus.
RT-PCR is the recommended test as others are unable to differentiate between pandemic H1N1 and regular seasonal flu. However, most people with flu symptoms do not need a test for pandemic H1N1 flu specifically, because the test results usually do not affect the recommended course of treatment. The U.S. CDC recommend testing only for people who are hospitalised with suspected flu, pregnant women and people with weakened immune systems. For the mere diagnosis of influenza and not pandemic H1N1 flu specifically, more widely available tests include rapid influenza diagnostic test
s (RIDT), which yield results in about 30 minutes, and direct
and indirect immunofluorescence
assays (DFA
and IFA), which take 2–4 hours. Due to the high rate of RIDT false negatives, the CDC advises that patients with illnesses compatible with novel influenza A (H1N1) virus infection but with negative RIDT results should be treated empirically based on the level of clinical suspicion, underlying medical conditions, severity of illness and risk for complications, and if a more definitive determination of infection with influenza virus is required, testing with rRT-PCR or virus isolation should be performed. Dr. Rhonda Medows of the Georgia
Department of Community Health states that the rapid tests are incorrect anywhere from 30% to 90% of the time and warns doctors in her state not to use them because they are wrong so often. The use of RIDTs has also been questioned by researcher Paul Schreckenberger of the Loyola University
Health System, who suggests that rapid tests may actually pose a dangerous public health
risk. Dr. Nikki Shindo of the WHO has expressed regret at reports of treatment being delayed by waiting for H1N1 test results and suggests, "[D]octors should not wait for the laboratory confirmation but make diagnosis based on clinical and epidemiological backgrounds and start treatment early".
On 22 June 2010, the CDC announced a new test called the "CDC Influenza 2009 A (H1N1)pdm Real-Time RT-PCR Panel (IVD)". It uses a molecular biology technique to detect influenza A viruses and specifically the 2009 H1N1 virus. The new test will replace the previous real-time RT-PCR diagnostic test used during the 2009 H1N1 pandemic, which received an emergency use authorisation from the U.S. Food and Drug Administration
in April 2009. Tests results are available in four hours and are 96% accurate.
against seasonal flu provided little protection. A study at the U.S. Centers for Disease Control and Prevention published in May 2009 found that children had no preexisting immunity to the new strain but that adults, particularly those over 60, had some degree of immunity
. Children showed no cross-reactive
antibody
reaction to the new strain, adults aged 18 to 64 had 6–9%, and older adults 33%. While it has been thought that these findings suggest the partial immunity in older adults may be due to previous exposure to similar seasonal influenza viruses, a November 2009 study of a rural unvaccinated population in China found only a 0.3% cross-reactive antibody reaction to the H1N1 strain, suggesting that previous vaccinations for seasonal flu and not exposure may have resulted in the immunity found in the older U.S. population.
It has been determined that the strain contains genes from five different flu viruses: North American swine influenza, North American avian influenza, human influenza and two swine influenza viruses typically found in Asia and Europe. Further analysis has shown that several protein
s of the virus are most similar to strains that cause mild symptoms in humans, leading virologist Wendy Barclay to suggest on 1 May 2009, that the initial indications are that the virus was unlikely to cause severe symptoms for most people.
The virus is currently less lethal than previous pandemic strains and kills about 0.01–0.03% of those infected; the 1918 influenza was about one hundred times more lethal and had a case fatality rate of 2–3%. By 14 November 2009, the virus had infected one in six Americans with 200,000 hospitalisations and 10,000 deaths – as many hospitalizations and fewer deaths than in an average flu season overall, but with much higher risk for those under 50. With deaths of 1,100 children and 7,500 adults 18 to 64, these figures "are much higher than in a usual flu season".
In June 2010, scientists from Hong Kong reported discovery of a new swine flu virus which is a hybrid of the pandemic H1N1 virus and viruses previously found in pigs. It is the first report of a reassortment of the pandemic virus, which in humans has been slow to evolve. Nancy Cox, head of the influenza division at the U.S. Centers for Disease Control and Prevention, has said, "This particular paper is extremely interesting because it demonstrates for the first time what we had worried about at the very onset of the pandemic, and that is that this particular virus, when introduced into pigs, could reassort with the resident viruses in pigs and we would have new gene constellations. And bingo, here we are." Pigs have been termed the mixing vessel of flu because they can be infected both by avian flu viruses, which rarely directly infect people, and by human viruses. When pigs become simultaneously infected with more than one virus, the viruses can swap genes, producing new variants which can pass to humans and sometimes spread amongst them. "Unlike the situation with birds and humans, we have a situation with pigs and humans where there's a two-way street of exchange of viruses. With pigs it's very much a two-way street".
The basic reproduction number
(the average number of other individuals whom each infected individual will infect, in a population which has no immunity to the disease) for the 2009 novel H1N1 is estimated to be 1.75. A December 2009 study found that the transmissibility of the H1N1 influenza virus in households is lower than that seen in past pandemics. Most transmissions occur soon before or after the onset of symptoms.
The H1N1 virus has been transmitted to animals, including swine, turkey
s, ferret
s, household cats, at least one dog and a cheetah
.
Although it was initially thought that two injections would be required, clinical trials showed that the new vaccine protected adults "with only one dose instead of two", and so the limited vaccine supplies would go twice as far as had been predicted. Health officials worldwide were also concerned because the virus was new and could easily mutate and become more virulent, even though most flu symptoms were mild and lasted only a few days without treatment. Officials also urged communities, businesses and individuals to make contingency plans for possible school closures, multiple employee absences for illness, surges of patients in hospitals and other effects of potentially widespread outbreaks.
In February 2010, the CDC's Advisory Committee on Immunization Practices voted for "universal" flu vaccination in the U.S. to include all people over six months of age. The 2010–2011 vaccine will protect against the 2009 H1N1 pandemic virus and two other flu viruses.
On 27 April 2009, the European Union
health commissioner advised Europeans to postpone nonessential travel to the United States or Mexico. This followed the discovery of the first confirmed case in Spain. On 6 May 2009, the Public Health Agency of Canada
announced that their National Microbiology Laboratory
(NML) had mapped the genetic code of the swine flu virus, the first time that had been done. In the U.K., the National Health Service
launched a website, the National Pandemic Flu Service, allowing patients to self-assess and get an authorisation number for antiviral medication. The system was expected to reduce the burden on general practitioner
s.
U.S. officials observed that six years of concern about H5N1
avian flu
did much to prepare for the current H1N1 flu outbreak, noting that after H5N1 emerged in Asia, ultimately killing about 60% of the few hundred people infected by it over the years, many countries took steps to try to prevent any similar crisis from spreading further. The CDC and other American governmental agencies used the summer lull to take stock of the United States' response to H1N1 flu and attempt to patch any gaps in the public health
safety net before flu season started in early autumn. Preparations included planning a second influenza vaccination program in addition to that for seasonal influenza, and improving coordination between federal, state and local governments and private health providers. On 24 October 2009, U.S. President Obama
declared swine flu a national emergency, giving Secretary of Health and Human Services Kathleen Sebelius
authority to grant waivers to requesting hospitals from usual federal requirements.
had been reported post-vaccination. Only a few of these were suspected to be actually related to the H1N1 vaccination, and only temporary illness had been observed. This is in strong contrast to the 1976 swine flu outbreak
, when mass vaccinations in the United States caused over 500 cases of Guillain-Barre syndrome and led to 25 deaths. Although the vaccines were effective, many industrialised nations were giving away, selling, canceling orders for and destroying excess doses of the vaccine.
There are safety concerns for people who are allergic to eggs because the viruses for the vaccine are grown in chicken-egg-based cultures. People with egg allergies may be able to receive the vaccine, after consultation with their physician, in graded doses in a careful and controlled environment. A vaccine manufactured by Baxter is made without using eggs, but requires two doses three weeks apart to produce immunity.
As of late November 2009, in Canada there had been 24 confirmed cases of anaphylactic shock following vaccination, including one death. The estimated rate is one anaphylactic reaction per 312,000 persons receiving the vaccine; however, six persons had suffered anaphylaxis out of 157,000 doses given from one batch of vaccine. Dr. David Butler-Jones, Canada's chief public health officer, stated that even though this was an adjuvant
ed vaccine, that did not appear to be the cause of this severe allergic reaction in these six patients.
, a German deputy who trained as a physician and now chairs the health committee at the Council of Europe
, claimed major firms had organised a "campaign of panic" to put pressure on the World Health Organisation (WHO) to declare a "false pandemic" to sell vaccines. Wodarg said the WHO's "false pandemic" flu campaign is "one of the greatest medicine scandals of the century". He said that the "false pandemic" campaign began last May in Mexico City
, when a hundred or so "normal" reported influenza cases were declared to be the beginning of a threatening new pandemic, although he said there was little scientific evidence for this. Nevertheless he argued that the WHO, "in cooperation with some big pharmaceutical companies and their scientists, re-defined pandemics", removing the statement that "an enormous amount of people have contracted the illness or died" from its existing definition and replacing it by stating simply that there has to be a virus, spreading beyond borders and to which people have no immunity. The WHO responded by stating that they take their duty to provide independent advice seriously and guarded against interference from outside interests. Announcing a review of the WHO's actions, spokeswoman Fadela Chaib stated: "Criticism is part of an outbreak cycle. We expect and indeed welcome criticism and the chance to discuss it". In March 2010, the Council of Europe
launched an enquiry into "the influence of the pharmaceutical companies on the global swine flu campaign", and a preliminary report is in preparation.
On 12 April 2010, Keiji Fukuda, the WHO's top influenza expert, stated that the system leading to the declaration of a pandemic led to confusion about H1N1 circulating around the world, and he expressed concern that there was a failure to communicate in regard to uncertainties about the new virus, which turned out to be not as deadly as feared. WHO Director-General Margaret Chan has appointed 29 flu experts from outside the organization to conduct a review of WHO's handling of the H1N1 flu pandemic. She has told them, "We want a frank, critical, transparent, credible and independent review of our performance".
In June 2010, Fiona Godlee
, editor-in-chief of the BMJ
, published an editorial which criticised the WHO, saying that an investigation had disclosed that some of the experts advising WHO on the pandemic had financial ties with drug companies which were producing antivirals and vaccines. Margaret Chan, Director-General of the WHO, replied stating, "Without question, the BMJ feature and editorial will leave many readers with the impression that WHO's decision to declare a pandemic was at least partially influenced by a desire to boost the profits of the pharmaceutical industry. The bottom line, however, is that decisions to raise the level of pandemic alert were based on clearly defined virological and epidemiological criteria. It is hard to bend these criteria, no matter what the motive". In August 2010, the Daily Mail
printed an article stating that "a third of the experts advising the World Health Organisation about the swine flu pandemic had ties to drugs firms" and that of the 20 members of the Scientific Advisory Group for Emergencies, which advised the British Government on swine flu, 11 had done work for the pharmaceutical industry or were linked to it through their universities.
On 7 May 2009, the WHO stated that containment was not feasible and that countries should focus on mitigating the effect of the virus. They did not recommend closing borders or restricting travel. On 26 April 2009, the Chinese government
announced that visitors returning from flu-affected areas who experienced flu-like symptoms within two weeks would be quarantined.
U.S. airlines had made no major changes as of the beginning of June 2009, but continued standing practices which include looking for passengers with symptoms of flu, measles
or other infections, and relying on in-flight air filter
s to ensure that aircraft were sanitised. Masks were not generally provided by airlines and the CDC did not recommend that airline crews wear them. Some non-U.S. airlines, mostly Asian, including Singapore Airlines
, China Eastern Airlines
, China Southern Airlines
, Cathay Pacific
and Mexicana Airlines, took measures such as stepping up cabin cleaning, installing state-of-the-art air filters and allowing in-flight staff to wear face masks.
The H1N1 outbreak led to numerous precautionary school closures in some areas. Rather than closing schools, the CDC recommended that students and school workers with flu symptoms should stay home for either seven days total, or until 24 hours after symptoms subsided, whichever was longer. The CDC also recommended that colleges should consider suspending fall 2009 classes if the virus began to cause severe illness in a significantly larger share of students than the previous spring. They also urged schools to suspend rules, such as penalties for late papers or missed classes or requirements for a doctor's note, to enforce "self-isolation" and prevent students from venturing out while ill; schools were advised to set aside a room for people developing flu-like symptoms while they waited to go home and to have ill students or staff and those caring for them use face masks.
In California, school districts and universities were on alert and working with health officials to launch education campaigns. Many planned to stockpile medical supplies and discuss worst-case scenarios, including plans to provide lessons and meals for low-income children in case elementary and secondary schools closed. University of California
campuses stockpiled supplies, from paper masks and hand sanitizer to food and water. To help prepare for contingencies, University of Maryland School of Medicine professor of pediatrics
James C. King Jr. suggested that every county should create an "influenza action team" to be run by the local health department
, parents and school administrators. , about 600 schools in the United States had been temporarily closed, affecting over 126,000 students in 19 states.
s.
The CDC estimated that as much as 40% of the workforce might be unable to work at the peak of the pandemic due to the need for many healthy adults to stay home and care for an ill family member, and advised that individuals should have steps in place should a workplace close down or a situation arise that requires working from home. The CDC further advised that persons in the workplace should stay home sick for seven days after getting the flu, or 24 hours after symptoms end, whichever is longer.
In the UK, the Health and Safety Executive
(HSE) also issued general guidance for employers.
The U.S. CDC does not recommend use of face masks or respirator
s in non-health care settings, such as schools, workplaces, or public places, with a few exceptions: people who are ill with the virus when around other people, and people who are at risk for severe illness while caring for someone with the flu. There has been some disagreement about the value of wearing facial masks, some experts fearing that masks may give people a false sense of security and should not replace other standard precautions. Masks may benefit people in close contact with infected persons, but it is unknown whether they prevent H1N1 flu infection. Yukihiro Nishiyama, professor of virology at Nagoya University
's School of Medicine, commented that the masks are "better than nothing, but it's hard to completely block out an airborne virus since it can easily slip through the gaps".
According to mask manufacturer 3M
, masks will filter out particles in industrial settings, but "there are no established exposure limits for biological agent
s such as swine flu virus". However, despite the lack of evidence of effectiveness, the use of such masks is common in Asia. They are particularly popular in Japan, where cleanliness and hygiene are highly valued and where etiquette obligates those who are sick to wear masks to avoid spreading disease.
s of foreign visitors suspected of having or being in contact with others who may have been infected. In May 2009, the Chinese government confined 21 U.S. students and three teachers to their hotel rooms. As a result, the US State Department issued a travel alert about China's anti-flu measures and warned travellers against travelling to China if ill. In Hong Kong, an entire hotel was quarantined with 240 guests; Australia ordered a cruise ship with 2,000 passengers to stay at sea because of a swine flu threat. Egypt
ian Muslims who went on the annual pilgrimage
to Mecca
risked being quarantined upon their return. Russia and Taiwan
said they would quarantine visitors with fevers who come from areas where the flu was present. Japan quarantined 47 airline passengers in a hotel for a week in mid-May, then in mid-June India suggested pre-screening "outbound" passengers from countries thought to have a high rate of infection.
have stressed that eating properly cooked pork or other food products derived from pigs will not cause flu. Nevertheless, on 27 April, Azerbaijan
imposed a ban on the importation of animal husbandry
products from America. The Indonesia
n government also halted the importation of pigs and initiated the examination of pigs in Indonesia. The Egyptian government ordered the slaughter of all pigs in Egypt on 29 April 2009.
pain medications such as acetaminophen and ibuprofen
do not kill the virus; however, they may be useful to reduce symptoms. Aspirin
and other salicylate products should not be used by people under 19 with any flu-type symptoms because of the risk of developing Reye's Syndrome
.
If the fever is mild and there are no other complications, fever medication is not recommended. Most people recover without medical attention, although those with pre-existing or underlying medical conditions are more prone to complications and may benefit from further treatments.
People in at-risk groups should be treated with antivirals (oseltamivir or zanamivir) as soon as possible when they first experience flu symptoms. The at-risk groups include pregnant and post partum women, children under two years old, and people with underlying conditions such as respiratory problems. People who are not in an at-risk group who have persistent or rapidly worsening symptoms should also be treated with antivirals. People who have developed pneumonia should be given both antivirals and antibiotics, as in many severe cases of H1N1-caused illness, bacterial infection develops. Antivirals are most useful if given within 48 hours of the start of symptoms and may improve outcomes in hospitalised patients. In those beyond 48 hours who are moderately or severely ill, antivirals may still be beneficial. If oseltamivir
(Tamiflu) is unavailable or cannot be used, zanamivir (Relenza) is recommended as a substitute. Peramivir
is an experimental antiviral drug
approved for hospitalised patients in cases where the other available methods of treatment are ineffective or unavailable.
To help avoid shortages of these drugs, the U.S. CDC recommended oseltamivir treatment primarily for people hospitalised with pandemic flu; people at risk of serious flu complications due to underlying medical conditions; and patients at risk of serious flu complications. The CDC warned that the indiscriminate use of antiviral medications to prevent and treat influenza could ease the way for drug-resistant strains to emerge, which would make the fight against the pandemic that much harder. In addition, a British report found that people often failed to complete a full course of the drug or took the medication when not needed.
(WHO) reported 314 samples of the 2009 pandemic H1N1 flu tested worldwide have shown resistance to oseltamivir
(Tamiflu). This is not totally unexpected as 99.6% of the seasonal H1N1 flu strains tested have developed resistance to oseltamivir. No circulating flu has yet shown any resistance to zanamivir (Relenza), the other available anti-viral.
, which reviews medical evidence, announced in a review published in BMJ
that it had reversed its previous findings that the antiviral drugs oseltamivir
(Tamiflu) and zanamivir (Relenza) can ward off pneumonia
and other serious conditions linked to influenza. They reported that an analysis of 20 studies showed oseltamivir offered mild benefits for healthy adults if taken within 24 hours of onset of symptoms, but found no clear evidence it prevented lower respiratory tract infections or other complications
of influenza. Their published finding relates only to its use in healthy adults with influenza; they say nothing about its use in patients judged to be at high risk of complications (pregnant women, children under five and those with underlying medical conditions), and uncertainty over its role in reducing complications in healthy adults may still leave it as a useful drug for reducing the duration of symptoms. The drugs might eventually be demonstrated to be effective against flu-related complications; in general, the Cochrane Collaboration concluded "Paucity of good data".
Some specific results from the BMJ article include: "The efficacy of oral oseltamivir against symptomatic laboratory confirmed influenza was 61% (risk ratio 0.39, 95% confidence interval 0.18 to 0.85) at daily ... The remaining evidence suggests oseltamivir did not reduce influenza related lower respiratory tract complications (risk ratio 0.55, 95% confidence interval 0.22 to 1.35)". Notice especially the wide range for this second result.
on 18 March 2009; immediately after the outbreak was officially announced, Mexico notified the U.S. and World Health Organization, and within days of the outbreak Mexico City was "effectively shut down". Some countries cancelled flights to Mexico while others halted trade. Calls to close the border to contain the spread were rejected. Mexico already had hundreds of non-lethal cases before the outbreak was officially discovered, and was therefore in the midst of a "silent epidemic". As a result, Mexico was reporting only the most serious cases which showed more severe signs different from those of normal flu, possibly leading to a skewed initial estimate of the case fatality rate.
, was confirmed from clinical specimens (nasopharyngeal
swab
) examined by the CDC on 14 April 2009. A second case, from nearby Imperial County, California
, was confirmed on 17 April. The patient in the first confirmed case had flu symptoms including fever and cough on clinical examination on 30 March, and the second on 28 March.
The first confirmed H1N1/09 pandemic flu death, which occurred at Texas Children's Hospital
in Houston, Texas, was of a toddler from Mexico City who was visiting family in Brownsville, Texas
, before being air-lifted to Houston for treatment.
With respect to the current H1N1 flu pandemic, influenza surveillance information is available but almost no studies have attempted to estimate the total number of deaths attributable to H1N1 flu. Two studies have been performed by the CDC, however; the most recent estimates that there were 9,820 deaths (range 7,070–13,930) attributable to H1N1 flu from April to 14 November 2009. During the same period, 1642 deaths were officially confirmed as caused by H1N1 flu. The WHO state that total mortality (including deaths unconfirmed or unreported) from H1N1 flu is "unquestionably higher" than their own confirmed death statistics.
The initial outbreak received a week of near-constant media attention. Epidemiologists cautioned that the number of cases reported in the early days of an outbreak can be very inaccurate and deceptive due to several causes, among them selection bias
, media bias
and incorrect reporting by governments. Inaccuracies could also be caused by authorities in different countries looking at differing population groups. Furthermore, countries with poor health care systems and older laboratory facilities may take longer to identify or report cases. "[E]ven in developed countries the [numbers of flu deaths] are uncertain, because medical authorities don't usually verify who actually died of influenza and who died of a flu-like illness". Dr. Joseph S. Bresee (the CDC flu division's epidemiology chief) and Dr. Michael Osterholm
(director of the Center for Infectious Disease Research and Policy
) have pointed out that millions of people have had H1N1 flu, usually in a mild form, so the numbers of laboratory-confirmed cases were actually meaningless, and in July 2009 the WHO stopped keeping count of individual cases and focused more on major outbreaks.
in September 2010, reported that findings showed that the 2009 H1N1 flu was no more severe than the seasonal flu. "The risk of most serious complications was not elevated in adults or children", the study's authors wrote. "Children were disproportionately affected by 2009 H1N1 infection, but the perceived severity of symptoms and risk of serious outcomes were not increased." Children infected in the 2009 H1N1 flu pandemic were no more likely to be hospitalized with complications or get pneumonia than those who catch seasonal strains. About 1.5% of children with the H1N1 swine flu strain were hospitalized within 30 days, compared with 3.7% of those sick with a seasonal strain of H1N1 and 3.1% with an H3N2 virus.
CDC illness and death estimates from April 2009 to April 2010, are as follows:
It is often stated that about 36,000 die from the seasonal flu in the U.S. each year, and this is frequently understood as an indication that the H1N1 strain was not as severe as seasonal influenza. The 36,000 estimate was presented in a 2003 study by CDC scientists published in the Journal of the American Medical Association but only refers to a period from 1990-91 through 1998-99. During those years, the number of estimated deaths ranged from 17,000 to 52,000, with an average of about 36,000. The JAMA study also looked at seasonal influenza-associated deaths over a 23 year period, from 1976-1977 and 1998-1999. During that period, estimates of respiratory and circulatory influenza-associated deaths ranged from about 5,000 to about 52,000, with an average of about 25,000. While the 36,000 number is often cited, it's important to note that during that decade, influenza A (H3N2) was the predominant virus during most of the seasons, and H3N2 influenza viruses are typically associated with higher death rates. CDC believes that the range of deaths over the past 31 years (~3,000 to ~49,000) is a more accurate representation of the unpredictability and variability of flu-associated deaths. The annual toll from seasonal influenza in the US is more accurately estimated at 3000-49,000 deaths per year. So the H1N1 pandemic estimated mortality of 8,870 to 18,300, places it in the mid-range of estimates.
The 2009 pandemic caused hospitals around the country to make significant preparations in terms of hospital surge capacities, especially within the emergency department and among vulnerable populations. In many cases, hospitals were relatively successful in making sure that those patients most severely affected by the influenza strain were able to be seen, treated, and discharged in an efficient manner. A proper case-study of the preparation, planning, mitigation, and response efforts during the Fall of 2009 is that of the Children's Hospital of Philadelphia (CHOP). For example, CHOP took several steps to increase the emergency department (ED) surge capacity response abilities through careful planning and mitigation efforts. To increase ED capacity and response, CHOP used portions of the main lobby area as an ED waiting room; several of the region's hospital-based outpatient facilities were in use during evening and weekend hours for non-emergent cases; the ED's 24-hour short-stay unit was utilized to care for ED patients in a longer-term capacity; non-board certified physicians (in pediatric emergency medicine) and inpatient-unit medical nurses were utilized for ED patient care; hospital units normally utilized for other medical or therapeutic purposes were transformed into ED patient rooms; and rooms normally used for only one patient were expanded to at least a capacity of 2
) differs in its tendency to affect younger, healthier people.
In addition to these annual epidemics, Influenza A virus strains caused three global pandemics during the 20th century: the Spanish flu in 1918, Asian flu
in 1957, and Hong Kong flu
in 1968–69. These virus strains had undergone major genetic changes
for which the population did not possess significant immunity
. Recent genetic analysis has revealed that three-quarters, or six out of the eight genetic segments, of the 2009 flu pandemic strain arose from the North American swine flu strains circulating since 1998, when a new strain was first identified on a factory farm in North Carolina, and which was the first-ever reported triple-hybrid flu virus.
The 1918 flu epidemic began with a wave of mild cases in the spring, followed by more deadly waves in the autumn, eventually killing hundreds of thousands in the United States. The great majority of deaths in the 1918 flu pandemic were the result of secondary bacterial pneumonia. The influenza virus damaged the lining of the bronchial tubes and lungs of victims, allowing common bacteria from the nose and throat to infect their lungs. Subsequent pandemics have had many fewer fatalities due to the development of antibiotic medicines which can treat pneumonia.
The influenza virus has also caused several pandemic threats over the past century, including the pseudo-pandemic of 1947 (thought of as mild because although globally distributed, it caused relatively few deaths), the 1976 swine flu outbreak
and the 1977 Russian flu, all caused by the H1N1 subtype. The world has been at an increased level of alert since the SARS
epidemic in Southeast Asia (caused by the SARS coronavirus
). The level of preparedness was further increased and sustained with the advent of the H5N1 bird flu outbreaks because of H5N1's high fatality rate, although the strains currently prevalent have limited human-to-human transmission (anthroponotic) capability, or epidemicity.
People who contracted flu before 1957 appeared to have some immunity to H1N1 flu. Dr. Daniel Jernigan, head of flu epidemiology for the U.S. CDC, has stated: "Tests on blood serum
from older people showed that they had antibodies that attacked the new virus ... That does not mean that everyone over 52 is immune, since Americans and Mexicans older than that have died of the new flu".
Influenza pandemic
An influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the human population. In contrast to the regular seasonal epidemics of influenza, these pandemics occur irregularly, with the 1918 Spanish flu the most serious pandemic in...
, and the second of the two pandemics involving H1N1 influenza virus (the first of them was the 1918 flu pandemic), albeit in a new version. First described in April 2009, the virus appeared to be a new strain of H1N1 which resulted when a previous triple reassortment
Reassortment
Reassortment is the mixing of the genetic material of a species into new combinations in different individuals. Several different processes contribute to reassortment, including assortment of chromosomes, and chromosomal crossover. It is particularly used when two similar viruses that are infecting...
of bird, swine and human flu viruses further combined with a Eurasian pig flu virus, leading to the term "swine flu
Swine flu
Swine influenza, also called pig influenza, swine flu, hog flu and pig flu, is an infection by any one of several types of swine influenza virus. Swine influenza virus or S-OIV is any strain of the influenza family of viruses that is endemic in pigs...
" to be used for this pandemic. Unlike most strains of influenza, H1N1 does not disproportionately infect adults older than 60 years; this was an unusual and characteristic feature of the H1N1 pandemic
Pandemic
A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic...
. Even in the case of previously very healthy persons, a small percentage will develop pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
or acute respiratory distress syndrome
Acute respiratory distress syndrome
Acute respiratory distress syndrome , also known as respiratory distress syndrome or adult respiratory distress syndrome is a serious reaction to various forms of injuries to the lung....
. This manifests itself as increased breathing difficulty and typically occurs 3–6 days after initial onset of flu symptoms. The pneumonia caused by flu can be either direct viral pneumonia or a secondary bacterial pneumonia. In fact, a November 2009 New England Journal of Medicine
New England Journal of Medicine
The New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It describes itself as the oldest continuously published medical journal in the world.-History:...
article recommends that flu patients whose chest X-ray indicates pneumonia receive both antivirals and antibiotics. In particular, it is a warning sign if a child (and presumably an adult) seems to be getting better and then relapses with high fever, as this relapse may be bacterial pneumonia.
Initially coined an "outbreak", the stint began in the state of Veracruz
Veracruz
Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is...
, Mexico, with evidence that there had been an ongoing epidemic for months before it was officially recognized as such. The Mexican government closed most of Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
's public and private facilities in an attempt to contain the spread of the virus; however, it continued to spread globally, and clinics in some areas were overwhelmed by infected people. In June, the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) and the U.S. Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
(CDC) stopped counting cases and declared the outbreak a pandemic
Pandemic
A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic...
.
Despite being informally called "swine flu", the H1N1 flu virus cannot be spread by eating pork or pork products; similar to other influenza viruses, it is typically contracted by person to person transmission through respiratory droplets. Symptoms usually last 4–6 days. Antivirals (oseltamivir
Oseltamivir
Oseltamivir INN , an antiviral drug, slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell; median time to symptom alleviation is reduced by 0.5–1 day. The drug is sold under the trade name Tamiflu, and is taken orally...
or zanamivir) were recommended for those with more severe symptoms or those in an at-risk group.
The pandemic began to taper off in November 2009, and by May 2010, the number of cases was in steep decline. On 10 August 2010, the Director-General of the World Health Organization, Margaret Chan
Margaret Chan
Margaret Chan Fung Fu-chun, OBE JP is the Director-General of the World Health Organization . Chan was elected by the Executive Board of the WHO on 8 November 2006, and was endorsed in a special meeting of the World Health Assembly on the following day...
, announced the end of the H1N1 pandemic, and announced that the H1N1 influenza event has moved into the post-pandemic period. According to the latest WHO statistics (July 2010), the virus has killed more than 18,000 people since it appeared in April 2009, however they state that the total mortality (including deaths unconfirmed or unreported) from the H1N1 strain is "unquestionably higher". Critics claimed the WHO had exaggerated the danger, spreading "fear and confusion" rather than "immediate information". The WHO began an investigation to determine whether it had "frightened people unnecessarily". A flu followup study done in September 2010, found that "the risk of most serious complications was not elevated in adults or children." In an August 5, 2011 PLoS ONE article, researchers estimated that the 2009 H1N1 global infection rate was 11% to 21%, lower than what was previously expected. Serbia's B92
B92
B92 is a radio and television broadcaster with national coverage headquartered in Belgrade, Serbia. The network's key demographic is chiefly urban and young audience. Its programs, including the news cover topics with fairly liberal political painted attitudes...
investigative reporting concluded that vaccine was not properly tested.
Classification
The initial outbreak was called the "H1N1 influenza", or "Swine Flu" by American media. It is called pandemic H1N1/09 virusPandemic H1N1/09 virus
The Pandemic H1N1/09 virus is a swine origin Influenza A virus subtype H1N1 virus strain responsible for the 2009 flu pandemic. For other names see the Nomenclature section below.-Virus characteristics:...
by the World Health Organization, while the U.S. Centers for Disease Control and Prevention refer to it as "novel influenza A (H1N1)" or "2009 H1N1 flu". In the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, it was originally called "Pig Flu", but is now called "New Influenza A (H1N1)" by the national health institute
Netherlands National Institute for Public Health and the Environment
The Netherlands National Institute for Public Health and the Environment , is a Dutch research institute that is an independent agency of the Dutch Ministry of Health, Welfare and Sport....
, although the media and general population use the name "Mexican Flu". South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
and Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
briefly considered calling it the "Mexican virus". Later, the South Korean press used "SI", short for "swine influenza". Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
suggested the names "H1N1 flu" or "new flu", which most local media adopted. The World Organization for Animal Health proposed the name "North American influenza". The European Commission
European Commission
The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
adopted the term "novel flu virus".
Signs and symptoms
The symptoms of H1N1 flu are similar to those of other influenzaInfluenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
s, and may include a fever, cough (typically a "dry cough"), headache, muscle
Myalgia
Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...
or joint
Arthralgia
Arthralgia literally means joint pain; it is a symptom of injury, infection, illnesses or an allergic reaction to medication....
pain, sore throat
Acute pharyngitis
Pharyngitis is an inflammation of the throat or pharynx. In most cases it is quite painful, and is the most common cause of a sore throat.Like many types of inflammation, pharyngitis can be acute – characterized by a rapid onset and typically a relatively short course – or chronic....
, chills
Rigor (medicine)
Rigor is a shaking occurring during a high fever. It occurs because cytokines and prostaglandins are released as part of an immune response and increase the set point for body temperature in the hypothalamus....
, fatigue, and runny nose
Rhinorrhea
Rhinorrhea or rhinorrhoea is a condition where the nasal cavity is filled with a significant amount of mucous fluid. The condition, commonly known as "runny nose", occurs relatively frequently and is not usually considered dangerous. Rhinorrhea is a common symptom of allergies or certain diseases,...
. Diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, vomiting, and neurological
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
problems have also been reported in some cases. People at higher risk of serious complications include those aged over 65, children younger than 5, children with neurodevelopmental conditions, pregnant women (especially during the third trimester), and those of any age with underlying medical conditions, such as asthma, diabetes, obesity, heart disease, or a weakened immune system (e.g., taking immunosuppressive medications or infected with HIV). More than 70% of hospitalizations in the U.S. have been people with such underlying conditions, according to the CDC.
In September 2009, the CDC reported that the H1N1 flu "seems to be taking a heavier toll among chronically ill children than the seasonal flu usually does." Through 8 August 2009, the CDC had received 36 reports of paediatric deaths with associated influenza symptoms and laboratory-confirmed pandemic H1N1 from state and local health authorities within the United States, with 22 of these children having neurodevelopmental conditions such as cerebral palsy
Cerebral palsy
Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....
, muscular dystrophy
Muscular dystrophy
Muscular dystrophy is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.In the 1860s, descriptions of boys who...
, or developmental delays. "Children with nerve and muscle problems may be at especially high risk for complications because they cannot cough hard enough to clear their airways". From 26 April 2009, to 13 February 2010, the CDC had received reports of the deaths of 277 children with laboratory-confirmed 2009 influenza A (H1N1) within the United States.
Symptoms in severe cases
The World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
reports that the clinical picture in severe cases is strikingly different from the disease pattern seen during epidemics of seasonal influenza. While people with certain underlying medical conditions are known to be at increased risk, many severe cases occur in previously healthy people. In severe cases, patients generally begin to deteriorate around three to five days after symptom onset. Deterioration is rapid, with many patients progressing to respiratory failure within 24 hours, requiring immediate admission to an intensive care unit. Upon admission, most patients need immediate respiratory support with mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
.
A November 2009 CDC recommendation stated that the following constitute "emergency warning signs" and advised seeking immediate care if a person experiences any one of these signs:
In adults
-
- Difficulty breathing or shortness of breath
- Pain or pressure in the chest or abdomen
- Sudden dizziness
- Confusion
- Severe or persistent vomiting
- Low temperature
In children
-
- Fast breathing or working hard to breathe
- Bluish skin color
- Not drinking enough fluids
- Not waking up or not interacting
- Being so irritable that the child does not want to be held
- Flu-like symptoms which improve but then return with fever and worse cough
- Fever with a rash
- Being unable to eat
- Having no tears when crying
Research later indicated that the severe flu effects in healthy young and middle-aged adults are caused by an excessive immune response.
Complications
Most complications have occurred among previously healthy individuals, with obesityObesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
and respiratory disease
Respiratory disease
Respiratory disease is a medical term that encompasses pathological conditions affecting the organs and tissues that make gas exchange possible in higher organisms, and includes conditions of the upper respiratory tract, trachea, bronchi, bronchioles, alveoli, pleura and pleural cavity, and the...
as the strongest risk factors. Pulmonary complications are common. Primary influenza pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
occurs most commonly in adults and may progress rapidly to acute lung injury requiring mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
. Secondary bacterial infection is more common in children. Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
, including methicillin-resistant strains, is an important cause of secondary bacterial pneumonia with a high mortality rate. Neuromuscular and cardiac complications are unusual but may occur.
A United Kingdom investigation of risk factors for hospitalisation and poor outcome with pandemic A/H1N1 influenza looked at 631 patients from 55 hospitals admitted with confirmed infection from May through September 2009. 13% were admitted to a high dependency or intensive care unit and 5% died; 36% were aged <16 years and 5% were aged ≥65 years. Non-white and pregnant patients were over-represented. 45% of patients had at least one underlying condition, mainly asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
, and 13% received antiviral drugs before admission. Of 349 with documented chest x-rays on admission, 29% had evidence of pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, but bacterial co-infection was uncommon. Multivariate analyses showed that physician-recorded obesity on admission and pulmonary conditions other than asthma or chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
(COPD) were associated with a severe outcome, as were radiologically confirmed pneumonia and a raised C-reactive protein
C-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
(CRP) level (≥. 59% of all in-hospital deaths occurred in previously healthy people.
Fulminant
Fulminant
Fulminant is any event or process that occurs suddenly and quickly, and is intense and severe to the point of lethality, i.e., it has an explosive character. The word comes from Latin fulmināre, to strike with lightning...
(sudden-onset) myocarditis
Myocarditis
Myocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...
has been linked to infection with H1N1, with at least four cases of myocarditis confirmed in patients also infected with A/H1N1. Three out of the four cases of H1N1-associated myocarditis were classified as fulminant, and one of the patients died.
Also, there appears to be a link between severe A/H1N1 influenza infection and pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
. In one report, five out of 14 patients admitted to the intensive care unit with severe A/H1N1 infection were found to have pulmonary emboli.
An article published in JAMA
Jama
Jama or JAMA may refer to:* Jama Software, a privately held company in Portland, Oregon* Journal of the American Medical Association, an international peer-reviewed general medical journal...
in September 2010 challenged previous reports and stated that children infected in the 2009 flu pandemic were no more likely to be hospitalised with complications or get pneumonia than those who catch seasonal strains. Researchers found that about 1.5% of children with the H1N1 swine flu strain were hospitalised within 30 days, compared with 3.7% of those sick with a seasonal strain of H1N1 and 3.1% with an H3N2 virus.
Diagnosis
Confirmed diagnosis of pandemic H1N1 flu requires testing of a nasopharyngeal, nasal or oropharyngeal tissue swab from the patient. Real-timeReal-time polymerase chain reaction
In molecular biology, real-time polymerase chain reaction, also called quantitative real time polymerase chain reaction or kinetic polymerase chain reaction , is a laboratory technique based on the PCR, which is used to amplify and simultaneously quantify a targeted DNA molecule...
RT-PCR is the recommended test as others are unable to differentiate between pandemic H1N1 and regular seasonal flu. However, most people with flu symptoms do not need a test for pandemic H1N1 flu specifically, because the test results usually do not affect the recommended course of treatment. The U.S. CDC recommend testing only for people who are hospitalised with suspected flu, pregnant women and people with weakened immune systems. For the mere diagnosis of influenza and not pandemic H1N1 flu specifically, more widely available tests include rapid influenza diagnostic test
Rapid influenza diagnostic test
A rapid influenza diagnostic test is a type of antigen detection test that detect influenza viral nucleoprotein antigen. Commercially available RIDTs can provide results within 30 minutes or less...
s (RIDT), which yield results in about 30 minutes, and direct
Direct fluorescent antibody
Direct fluorescent antibody is a laboratory test that uses antibodies tagged with fluorescent dye that can be used to detect the presence of microorganisms. This method offers straightforward detection of antigens using fluorescently labeled antigen-specific antibodies...
and indirect immunofluorescence
Immunofluorescence
Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows...
assays (DFA
Direct fluorescent antibody
Direct fluorescent antibody is a laboratory test that uses antibodies tagged with fluorescent dye that can be used to detect the presence of microorganisms. This method offers straightforward detection of antigens using fluorescently labeled antigen-specific antibodies...
and IFA), which take 2–4 hours. Due to the high rate of RIDT false negatives, the CDC advises that patients with illnesses compatible with novel influenza A (H1N1) virus infection but with negative RIDT results should be treated empirically based on the level of clinical suspicion, underlying medical conditions, severity of illness and risk for complications, and if a more definitive determination of infection with influenza virus is required, testing with rRT-PCR or virus isolation should be performed. Dr. Rhonda Medows of the Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
Department of Community Health states that the rapid tests are incorrect anywhere from 30% to 90% of the time and warns doctors in her state not to use them because they are wrong so often. The use of RIDTs has also been questioned by researcher Paul Schreckenberger of the Loyola University
Loyola University Chicago
Loyola University Chicago is a private Jesuit research university located in Chicago, Illinois, United States. Founded by the Society of Jesus in 1870 under the title St...
Health System, who suggests that rapid tests may actually pose a dangerous public health
Public health
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals" . It is concerned with threats to health based on population health...
risk. Dr. Nikki Shindo of the WHO has expressed regret at reports of treatment being delayed by waiting for H1N1 test results and suggests, "[D]octors should not wait for the laboratory confirmation but make diagnosis based on clinical and epidemiological backgrounds and start treatment early".
On 22 June 2010, the CDC announced a new test called the "CDC Influenza 2009 A (H1N1)pdm Real-Time RT-PCR Panel (IVD)". It uses a molecular biology technique to detect influenza A viruses and specifically the 2009 H1N1 virus. The new test will replace the previous real-time RT-PCR diagnostic test used during the 2009 H1N1 pandemic, which received an emergency use authorisation from the U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
in April 2009. Tests results are available in four hours and are 96% accurate.
Virus characteristics
The virus was found to be a novel strain of influenza for which extant vaccinesVaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
against seasonal flu provided little protection. A study at the U.S. Centers for Disease Control and Prevention published in May 2009 found that children had no preexisting immunity to the new strain but that adults, particularly those over 60, had some degree of immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
. Children showed no cross-reactive
Cross-reactivity
Cross-reactivity is the reaction between an antibody and an antigen that differs from the immunogen. It is sometimes also referred to as crossimmunity or cross-protective immunity...
antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
reaction to the new strain, adults aged 18 to 64 had 6–9%, and older adults 33%. While it has been thought that these findings suggest the partial immunity in older adults may be due to previous exposure to similar seasonal influenza viruses, a November 2009 study of a rural unvaccinated population in China found only a 0.3% cross-reactive antibody reaction to the H1N1 strain, suggesting that previous vaccinations for seasonal flu and not exposure may have resulted in the immunity found in the older U.S. population.
It has been determined that the strain contains genes from five different flu viruses: North American swine influenza, North American avian influenza, human influenza and two swine influenza viruses typically found in Asia and Europe. Further analysis has shown that several protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s of the virus are most similar to strains that cause mild symptoms in humans, leading virologist Wendy Barclay to suggest on 1 May 2009, that the initial indications are that the virus was unlikely to cause severe symptoms for most people.
The virus is currently less lethal than previous pandemic strains and kills about 0.01–0.03% of those infected; the 1918 influenza was about one hundred times more lethal and had a case fatality rate of 2–3%. By 14 November 2009, the virus had infected one in six Americans with 200,000 hospitalisations and 10,000 deaths – as many hospitalizations and fewer deaths than in an average flu season overall, but with much higher risk for those under 50. With deaths of 1,100 children and 7,500 adults 18 to 64, these figures "are much higher than in a usual flu season".
In June 2010, scientists from Hong Kong reported discovery of a new swine flu virus which is a hybrid of the pandemic H1N1 virus and viruses previously found in pigs. It is the first report of a reassortment of the pandemic virus, which in humans has been slow to evolve. Nancy Cox, head of the influenza division at the U.S. Centers for Disease Control and Prevention, has said, "This particular paper is extremely interesting because it demonstrates for the first time what we had worried about at the very onset of the pandemic, and that is that this particular virus, when introduced into pigs, could reassort with the resident viruses in pigs and we would have new gene constellations. And bingo, here we are." Pigs have been termed the mixing vessel of flu because they can be infected both by avian flu viruses, which rarely directly infect people, and by human viruses. When pigs become simultaneously infected with more than one virus, the viruses can swap genes, producing new variants which can pass to humans and sometimes spread amongst them. "Unlike the situation with birds and humans, we have a situation with pigs and humans where there's a two-way street of exchange of viruses. With pigs it's very much a two-way street".
Transmission
Spread of the H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza. Sometimes people may become infected by touching something – such as a surface or object – with flu viruses on it and then touching their face. "Avoid touching your eyes, nose or mouth. Germs spread this way".The basic reproduction number
Basic reproduction number
In epidemiology, the basic reproduction number of an infection is the mean number of secondary cases caused by an individual infected soon after disease introduction into a population with no pre-existing immunity to the disease in the absence of interventions to control...
(the average number of other individuals whom each infected individual will infect, in a population which has no immunity to the disease) for the 2009 novel H1N1 is estimated to be 1.75. A December 2009 study found that the transmissibility of the H1N1 influenza virus in households is lower than that seen in past pandemics. Most transmissions occur soon before or after the onset of symptoms.
The H1N1 virus has been transmitted to animals, including swine, turkey
Turkey (bird)
A turkey is a large bird in the genus Meleagris. One species, Meleagris gallopavo, commonly known as the Wild Turkey, is native to the forests of North America. The domestic turkey is a descendant of this species...
s, ferret
Ferret
The ferret is a domesticated mammal of the type Mustela putorius furo. Ferrets are sexually dimorphic predators with males being substantially larger than females. They typically have brown, black, white, or mixed fur...
s, household cats, at least one dog and a cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...
.
Prevention
The H1N1 vaccine was initially in short supply and in the U.S., the CDC recommended that initial doses should go to priority groups such as pregnant women, people who live with or care for babies under six months old, children six months to four years old and health-care workers. In the UK, the NHS recommended vaccine priority go to people over six months old who were clinically at risk for seasonal flu, pregnant women and households of people with compromised immunity.Although it was initially thought that two injections would be required, clinical trials showed that the new vaccine protected adults "with only one dose instead of two", and so the limited vaccine supplies would go twice as far as had been predicted. Health officials worldwide were also concerned because the virus was new and could easily mutate and become more virulent, even though most flu symptoms were mild and lasted only a few days without treatment. Officials also urged communities, businesses and individuals to make contingency plans for possible school closures, multiple employee absences for illness, surges of patients in hospitals and other effects of potentially widespread outbreaks.
In February 2010, the CDC's Advisory Committee on Immunization Practices voted for "universal" flu vaccination in the U.S. to include all people over six months of age. The 2010–2011 vaccine will protect against the 2009 H1N1 pandemic virus and two other flu viruses.
Public health response
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
health commissioner advised Europeans to postpone nonessential travel to the United States or Mexico. This followed the discovery of the first confirmed case in Spain. On 6 May 2009, the Public Health Agency of Canada
Public Health Agency of Canada
The Public Health Agency of Canada is an agency of the Government of Canada that is responsible for public health, emergency preparedness, and response and infectious and chronic disease control and prevention...
announced that their National Microbiology Laboratory
National Microbiology Laboratory
The National Microbiology Laboratory is a division of the Public Health Agency of Canada that is located in the Canadian Science Centre for Human and Animal Health in Winnipeg, Manitoba. This modern state-of-the-art facility houses the NML's Biological Safety Level 4 containment laboratory,...
(NML) had mapped the genetic code of the swine flu virus, the first time that had been done. In the U.K., the National Health Service
National Health Service
The National Health Service is the shared name of three of the four publicly funded healthcare systems in the United Kingdom. They provide a comprehensive range of health services, the vast majority of which are free at the point of use to residents of the United Kingdom...
launched a website, the National Pandemic Flu Service, allowing patients to self-assess and get an authorisation number for antiviral medication. The system was expected to reduce the burden on general practitioner
General practitioner
A general practitioner is a medical practitioner who treats acute and chronic illnesses and provides preventive care and health education for all ages and both sexes. They have particular skills in treating people with multiple health issues and comorbidities...
s.
U.S. officials observed that six years of concern about H5N1
H5N1
Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
avian flu
Avian flu
Avian influenza, sometimes avian flu, and commonly bird flu, refers to "influenza caused by viruses adapted to birds." Of the greatest concern is highly pathogenic avian influenza ....
did much to prepare for the current H1N1 flu outbreak, noting that after H5N1 emerged in Asia, ultimately killing about 60% of the few hundred people infected by it over the years, many countries took steps to try to prevent any similar crisis from spreading further. The CDC and other American governmental agencies used the summer lull to take stock of the United States' response to H1N1 flu and attempt to patch any gaps in the public health
Public health
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals" . It is concerned with threats to health based on population health...
safety net before flu season started in early autumn. Preparations included planning a second influenza vaccination program in addition to that for seasonal influenza, and improving coordination between federal, state and local governments and private health providers. On 24 October 2009, U.S. President Obama
Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...
declared swine flu a national emergency, giving Secretary of Health and Human Services Kathleen Sebelius
Kathleen Sebelius
Kathleen Sebelius is an American politician currently serving as the 21st Secretary of Health and Human Services. She was the second female Governor of Kansas from 2003 to 2009, the Democratic respondent to the 2008 State of the Union address, and chair-emerita of the Democratic Governors...
authority to grant waivers to requesting hospitals from usual federal requirements.
Vaccines
, over doses of vaccine had been administered in over 16 countries; the vaccine seems safe and effective, producing a strong immune response that should protect against infection. Whereas the 2009 trivalent seasonal influenza vaccine neither increases nor decreases the risk of infection with H1N1, the vaccines rushed to combat the new strain are effective against H1N1, although they are manufactured similarly. Overall the safety profile of the new H1N1 vaccine is similar to that of the seasonal flu vaccine, and as of November 2009 fewer than a dozen cases of Guillain-Barre syndromeGuillain-Barré syndrome
Guillain–Barré syndrome , sometimes called Landry's paralysis, is an acute inflammatory demyelinating polyneuropathy , a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom...
had been reported post-vaccination. Only a few of these were suspected to be actually related to the H1N1 vaccination, and only temporary illness had been observed. This is in strong contrast to the 1976 swine flu outbreak
1976 swine flu outbreak
The 1976 swine flu outbreak, also known as the swine flu fiasco, or the swine flu debacle, was a strain of H1N1 influenza virus that appeared in 1976. Infections were only detected from January 19 to February 9, and were not found outside Fort Dix. The outbreak is most remembered for the mass...
, when mass vaccinations in the United States caused over 500 cases of Guillain-Barre syndrome and led to 25 deaths. Although the vaccines were effective, many industrialised nations were giving away, selling, canceling orders for and destroying excess doses of the vaccine.
There are safety concerns for people who are allergic to eggs because the viruses for the vaccine are grown in chicken-egg-based cultures. People with egg allergies may be able to receive the vaccine, after consultation with their physician, in graded doses in a careful and controlled environment. A vaccine manufactured by Baxter is made without using eggs, but requires two doses three weeks apart to produce immunity.
As of late November 2009, in Canada there had been 24 confirmed cases of anaphylactic shock following vaccination, including one death. The estimated rate is one anaphylactic reaction per 312,000 persons receiving the vaccine; however, six persons had suffered anaphylaxis out of 157,000 doses given from one batch of vaccine. Dr. David Butler-Jones, Canada's chief public health officer, stated that even though this was an adjuvant
Adjuvant
An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents, such as a drug or vaccine, while having few if any direct effects when given by itself...
ed vaccine, that did not appear to be the cause of this severe allergic reaction in these six patients.
Accusations of conflict of interest
In January 2010, Wolfgang WodargWolfgang Wodarg
Wolfgang Wodarg is a German physician and politician for SPD.As chairman of the Parliamentary Assembly of the Council of Europe Health Committee Wodarg co-signed a proposed resolution on December 18, 2009, which will be discussed in January in an emergency debate and he has called for an inquiry...
, a German deputy who trained as a physician and now chairs the health committee at the Council of Europe
Council of Europe
The Council of Europe is an international organisation promoting co-operation between all countries of Europe in the areas of legal standards, human rights, democratic development, the rule of law and cultural co-operation...
, claimed major firms had organised a "campaign of panic" to put pressure on the World Health Organisation (WHO) to declare a "false pandemic" to sell vaccines. Wodarg said the WHO's "false pandemic" flu campaign is "one of the greatest medicine scandals of the century". He said that the "false pandemic" campaign began last May in Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
, when a hundred or so "normal" reported influenza cases were declared to be the beginning of a threatening new pandemic, although he said there was little scientific evidence for this. Nevertheless he argued that the WHO, "in cooperation with some big pharmaceutical companies and their scientists, re-defined pandemics", removing the statement that "an enormous amount of people have contracted the illness or died" from its existing definition and replacing it by stating simply that there has to be a virus, spreading beyond borders and to which people have no immunity. The WHO responded by stating that they take their duty to provide independent advice seriously and guarded against interference from outside interests. Announcing a review of the WHO's actions, spokeswoman Fadela Chaib stated: "Criticism is part of an outbreak cycle. We expect and indeed welcome criticism and the chance to discuss it". In March 2010, the Council of Europe
Council of Europe
The Council of Europe is an international organisation promoting co-operation between all countries of Europe in the areas of legal standards, human rights, democratic development, the rule of law and cultural co-operation...
launched an enquiry into "the influence of the pharmaceutical companies on the global swine flu campaign", and a preliminary report is in preparation.
On 12 April 2010, Keiji Fukuda, the WHO's top influenza expert, stated that the system leading to the declaration of a pandemic led to confusion about H1N1 circulating around the world, and he expressed concern that there was a failure to communicate in regard to uncertainties about the new virus, which turned out to be not as deadly as feared. WHO Director-General Margaret Chan has appointed 29 flu experts from outside the organization to conduct a review of WHO's handling of the H1N1 flu pandemic. She has told them, "We want a frank, critical, transparent, credible and independent review of our performance".
In June 2010, Fiona Godlee
Fiona Godlee
Fiona Godlee has been editor in chief of the BMJ since 2005; she is the first female editor appointed in the journal's history.-Career:...
, editor-in-chief of the BMJ
BMJ
BMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
, published an editorial which criticised the WHO, saying that an investigation had disclosed that some of the experts advising WHO on the pandemic had financial ties with drug companies which were producing antivirals and vaccines. Margaret Chan, Director-General of the WHO, replied stating, "Without question, the BMJ feature and editorial will leave many readers with the impression that WHO's decision to declare a pandemic was at least partially influenced by a desire to boost the profits of the pharmaceutical industry. The bottom line, however, is that decisions to raise the level of pandemic alert were based on clearly defined virological and epidemiological criteria. It is hard to bend these criteria, no matter what the motive". In August 2010, the Daily Mail
Daily Mail
The Daily Mail is a British daily middle-market tabloid newspaper owned by the Daily Mail and General Trust. First published in 1896 by Lord Northcliffe, it is the United Kingdom's second biggest-selling daily newspaper after The Sun. Its sister paper The Mail on Sunday was launched in 1982...
printed an article stating that "a third of the experts advising the World Health Organisation about the swine flu pandemic had ties to drugs firms" and that of the 20 members of the Scientific Advisory Group for Emergencies, which advised the British Government on swine flu, 11 had done work for the pharmaceutical industry or were linked to it through their universities.
Travel precautions
Government of the People's Republic of China
All power within the government of the People's Republic of China is divided among three bodies: the People's Republic of China, State Council, and the People's Liberation Army . This article is concerned with the formal structure of the state, its departments and their responsibilities...
announced that visitors returning from flu-affected areas who experienced flu-like symptoms within two weeks would be quarantined.
U.S. airlines had made no major changes as of the beginning of June 2009, but continued standing practices which include looking for passengers with symptoms of flu, measles
Measles
Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
or other infections, and relying on in-flight air filter
Air filter
A particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. A chemical air filter consists of an absorbent or catalyst for the removal of airborne molecular contaminants such as volatile organic compounds...
s to ensure that aircraft were sanitised. Masks were not generally provided by airlines and the CDC did not recommend that airline crews wear them. Some non-U.S. airlines, mostly Asian, including Singapore Airlines
Singapore Airlines
Singapore Airlines Limited is the flag carrier airline of Singapore. Singapore Airlines operates a hub at Changi Airport and has a strong presence in the Southeast Asia, East Asia, South Asia, and "Kangaroo Route" markets...
, China Eastern Airlines
China Eastern Airlines
China Eastern Airlines Corporation Limited is an airline headquartered on the grounds of Shanghai Hongqiao International Airport in Changning District, Shanghai, China. It is a major Chinese airline operating international, domestic and regional routes. Its main hubs are at Shanghai Pudong...
, China Southern Airlines
China Southern Airlines
China Southern Airlines is an airline headquartered in Baiyun District, Guangzhou, Guangdong Province, People's Republic of China. It is the world's sixth-largest airline measured by passengers carried, and Asia's largest airline in terms of both fleet size and passengers carried...
, Cathay Pacific
Cathay Pacific
Cathay Pacific is the flag carrier of Hong Kong, with its head office and main hub located at Hong Kong International Airport, although the airline's registered office is on the 33rd floor of One Pacific Place...
and Mexicana Airlines, took measures such as stepping up cabin cleaning, installing state-of-the-art air filters and allowing in-flight staff to wear face masks.
Schools
U.S. government officials have been especially concerned about schools because the H1N1 flu virus appears to disproportionately affect young and school-age people, between six months and 24 years of age.The H1N1 outbreak led to numerous precautionary school closures in some areas. Rather than closing schools, the CDC recommended that students and school workers with flu symptoms should stay home for either seven days total, or until 24 hours after symptoms subsided, whichever was longer. The CDC also recommended that colleges should consider suspending fall 2009 classes if the virus began to cause severe illness in a significantly larger share of students than the previous spring. They also urged schools to suspend rules, such as penalties for late papers or missed classes or requirements for a doctor's note, to enforce "self-isolation" and prevent students from venturing out while ill; schools were advised to set aside a room for people developing flu-like symptoms while they waited to go home and to have ill students or staff and those caring for them use face masks.
In California, school districts and universities were on alert and working with health officials to launch education campaigns. Many planned to stockpile medical supplies and discuss worst-case scenarios, including plans to provide lessons and meals for low-income children in case elementary and secondary schools closed. University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...
campuses stockpiled supplies, from paper masks and hand sanitizer to food and water. To help prepare for contingencies, University of Maryland School of Medicine professor of pediatrics
Pediatrics
Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...
James C. King Jr. suggested that every county should create an "influenza action team" to be run by the local health department
Health department
A health department or health ministry is a part of government which focuses on issues related to the general health of the citizenry. Subnational entities, such as states, counties and cities, often also operate a health department of their own...
, parents and school administrators. , about 600 schools in the United States had been temporarily closed, affecting over 126,000 students in 19 states.
Workplace
Fearing a worst-case scenario, the U.S. Department of Health and Human Services (HHS), the Centers for Disease Control and Prevention and the Department of Homeland Security (DHS) developed updated guidance and a video for employers to use as they developed plans to respond to the H1N1 outbreak. The guidance suggested that employers consider and communicate their objectives, such as reducing transmission among staff, protecting people who are at increased risk of influenza-related complications from becoming infected, maintaining business operations, and minimising adverse effects on other entities in their supply chainSupply chain
A supply chain is a system of organizations, people, technology, activities, information and resources involved in moving a product or service from supplier to customer. Supply chain activities transform natural resources, raw materials and components into a finished product that is delivered to...
s.
The CDC estimated that as much as 40% of the workforce might be unable to work at the peak of the pandemic due to the need for many healthy adults to stay home and care for an ill family member, and advised that individuals should have steps in place should a workplace close down or a situation arise that requires working from home. The CDC further advised that persons in the workplace should stay home sick for seven days after getting the flu, or 24 hours after symptoms end, whichever is longer.
In the UK, the Health and Safety Executive
Health and Safety Executive
The Health and Safety Executive is a non-departmental public body in the United Kingdom. It is the body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare, and for research into occupational risks in England and Wales and Scotland...
(HSE) also issued general guidance for employers.
Facial masks
Respirator
A respirator is a device designed to protect the wearer from inhaling harmful dusts, fumes, vapors, or gases. Respirators come in a wide range of types and sizes used by the military, private industry, and the public...
s in non-health care settings, such as schools, workplaces, or public places, with a few exceptions: people who are ill with the virus when around other people, and people who are at risk for severe illness while caring for someone with the flu. There has been some disagreement about the value of wearing facial masks, some experts fearing that masks may give people a false sense of security and should not replace other standard precautions. Masks may benefit people in close contact with infected persons, but it is unknown whether they prevent H1N1 flu infection. Yukihiro Nishiyama, professor of virology at Nagoya University
Nagoya University
Nagoya University is one of the most prestigious universities in Japan. It can be seen in the several rankings such as shown below.-General Rankings:...
's School of Medicine, commented that the masks are "better than nothing, but it's hard to completely block out an airborne virus since it can easily slip through the gaps".
According to mask manufacturer 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
, masks will filter out particles in industrial settings, but "there are no established exposure limits for biological agent
Biological agent
A biological agent — also called bio-agent or biological threat agent — is a bacterium, virus, prion, or fungus which may cause infection, allergy, toxicity or otherwise create a hazard to human health. They can be used as a biological weapon in bioterrorism or biological warfare...
s such as swine flu virus". However, despite the lack of evidence of effectiveness, the use of such masks is common in Asia. They are particularly popular in Japan, where cleanliness and hygiene are highly valued and where etiquette obligates those who are sick to wear masks to avoid spreading disease.
Quarantine
During the height of the fear of a pandemic, some countries initiated or threatened to initiate quarantineQuarantine
Quarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....
s of foreign visitors suspected of having or being in contact with others who may have been infected. In May 2009, the Chinese government confined 21 U.S. students and three teachers to their hotel rooms. As a result, the US State Department issued a travel alert about China's anti-flu measures and warned travellers against travelling to China if ill. In Hong Kong, an entire hotel was quarantined with 240 guests; Australia ordered a cruise ship with 2,000 passengers to stay at sea because of a swine flu threat. Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
ian Muslims who went on the annual pilgrimage
Pilgrimage
A pilgrimage is a journey or search of great moral or spiritual significance. Typically, it is a journey to a shrine or other location of importance to a person's beliefs and faith...
to Mecca
Mecca
Mecca is a city in the Hijaz and the capital of Makkah province in Saudi Arabia. The city is located inland from Jeddah in a narrow valley at a height of above sea level...
risked being quarantined upon their return. Russia and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
said they would quarantine visitors with fevers who come from areas where the flu was present. Japan quarantined 47 airline passengers in a hotel for a week in mid-May, then in mid-June India suggested pre-screening "outbound" passengers from countries thought to have a high rate of infection.
Pigs and food safety
The pandemic virus is a type of swine influenza, derived originally from a strain which lived in pigs, and this origin gave rise to the common name of "swine flu". This term is widely used by mass media. The virus has been found in American hogs, and Canadian as well as in hogs in Northern Ireland, Argentina, and Norway. Leading health agencies and the United States Secretary of AgricultureUnited States Secretary of Agriculture
The United States Secretary of Agriculture is the head of the United States Department of Agriculture. The current secretary is Tom Vilsack, who was confirmed by the U.S. Senate on 20 January 2009. The position carries similar responsibilities to those of agriculture ministers in other...
have stressed that eating properly cooked pork or other food products derived from pigs will not cause flu. Nevertheless, on 27 April, Azerbaijan
Azerbaijan
Azerbaijan , officially the Republic of Azerbaijan is the largest country in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west, and Iran to...
imposed a ban on the importation of animal husbandry
Animal husbandry
Animal husbandry is the agricultural practice of breeding and raising livestock.- History :Animal husbandry has been practiced for thousands of years, since the first domestication of animals....
products from America. The Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
n government also halted the importation of pigs and initiated the examination of pigs in Indonesia. The Egyptian government ordered the slaughter of all pigs in Egypt on 29 April 2009.
Treatment
A number of methods have been recommended to help ease symptoms, including adequate liquid intake and rest. Over-the-counterOver-the-counter drug
Over-the-counter drugs are medicines that may be sold directly to a consumer without a prescription from a healthcare professional, as compared to prescription drugs, which may be sold only to consumers possessing a valid prescription...
pain medications such as acetaminophen and ibuprofen
Ibuprofen
Ibuprofen is a nonsteroidal anti-inflammatory drug used for relief of symptoms of arthritis, fever, as an analgesic , especially where there is an inflammatory component, and dysmenorrhea....
do not kill the virus; however, they may be useful to reduce symptoms. Aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
and other salicylate products should not be used by people under 19 with any flu-type symptoms because of the risk of developing Reye's Syndrome
Reye's syndrome
Reye's syndrome is a potentially fatal disease that causes numerous detrimental effects to many organs, especially the brain and liver, as well as causing a lower than usual level of blood sugar . The classic features are liver damage, aspirin use and a viral infection...
.
If the fever is mild and there are no other complications, fever medication is not recommended. Most people recover without medical attention, although those with pre-existing or underlying medical conditions are more prone to complications and may benefit from further treatments.
People in at-risk groups should be treated with antivirals (oseltamivir or zanamivir) as soon as possible when they first experience flu symptoms. The at-risk groups include pregnant and post partum women, children under two years old, and people with underlying conditions such as respiratory problems. People who are not in an at-risk group who have persistent or rapidly worsening symptoms should also be treated with antivirals. People who have developed pneumonia should be given both antivirals and antibiotics, as in many severe cases of H1N1-caused illness, bacterial infection develops. Antivirals are most useful if given within 48 hours of the start of symptoms and may improve outcomes in hospitalised patients. In those beyond 48 hours who are moderately or severely ill, antivirals may still be beneficial. If oseltamivir
Oseltamivir
Oseltamivir INN , an antiviral drug, slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell; median time to symptom alleviation is reduced by 0.5–1 day. The drug is sold under the trade name Tamiflu, and is taken orally...
(Tamiflu) is unavailable or cannot be used, zanamivir (Relenza) is recommended as a substitute. Peramivir
Peramivir
Peramivir is an experimental antiviral drug developed by BioCryst Pharmaceuticals for the treatment of influenza. It has been authorized for the emergency use of treatment of certain hospitalized patients with known or suspected 2009 H1N1 influenza....
is an experimental antiviral drug
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
approved for hospitalised patients in cases where the other available methods of treatment are ineffective or unavailable.
To help avoid shortages of these drugs, the U.S. CDC recommended oseltamivir treatment primarily for people hospitalised with pandemic flu; people at risk of serious flu complications due to underlying medical conditions; and patients at risk of serious flu complications. The CDC warned that the indiscriminate use of antiviral medications to prevent and treat influenza could ease the way for drug-resistant strains to emerge, which would make the fight against the pandemic that much harder. In addition, a British report found that people often failed to complete a full course of the drug or took the medication when not needed.
Side effects
Both medications have known side effects, including lightheadedness, chills, nausea, vomiting, loss of appetite and trouble breathing. Children were reported to be at increased risk of self-injury and confusion after taking oseltamivir. The WHO warn against buying antiviral medications from online sources, and estimate that half the drugs sold by online pharmacies without a physical address are counterfeit.Resistance
, the World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) reported 314 samples of the 2009 pandemic H1N1 flu tested worldwide have shown resistance to oseltamivir
Oseltamivir
Oseltamivir INN , an antiviral drug, slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell; median time to symptom alleviation is reduced by 0.5–1 day. The drug is sold under the trade name Tamiflu, and is taken orally...
(Tamiflu). This is not totally unexpected as 99.6% of the seasonal H1N1 flu strains tested have developed resistance to oseltamivir. No circulating flu has yet shown any resistance to zanamivir (Relenza), the other available anti-viral.
Effectiveness of antivirals questioned
On 8 December 2009, the Cochrane CollaborationCochrane Collaboration
The Cochrane Collaboration is a group of over 28,000 volunteers in more than 100 countries who review the effects of health care interventions tested in biomedical randomized controlled trials. A few more recent reviews have also studied the results of non-randomized, observational studies...
, which reviews medical evidence, announced in a review published in BMJ
BMJ
BMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
that it had reversed its previous findings that the antiviral drugs oseltamivir
Oseltamivir
Oseltamivir INN , an antiviral drug, slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell; median time to symptom alleviation is reduced by 0.5–1 day. The drug is sold under the trade name Tamiflu, and is taken orally...
(Tamiflu) and zanamivir (Relenza) can ward off pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
and other serious conditions linked to influenza. They reported that an analysis of 20 studies showed oseltamivir offered mild benefits for healthy adults if taken within 24 hours of onset of symptoms, but found no clear evidence it prevented lower respiratory tract infections or other complications
Complication (medicine)
Complication, in medicine, is an unfavorable evolution of a disease, a health condition or a medical treatment. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A...
of influenza. Their published finding relates only to its use in healthy adults with influenza; they say nothing about its use in patients judged to be at high risk of complications (pregnant women, children under five and those with underlying medical conditions), and uncertainty over its role in reducing complications in healthy adults may still leave it as a useful drug for reducing the duration of symptoms. The drugs might eventually be demonstrated to be effective against flu-related complications; in general, the Cochrane Collaboration concluded "Paucity of good data".
Some specific results from the BMJ article include: "The efficacy of oral oseltamivir against symptomatic laboratory confirmed influenza was 61% (risk ratio 0.39, 95% confidence interval 0.18 to 0.85) at daily ... The remaining evidence suggests oseltamivir did not reduce influenza related lower respiratory tract complications (risk ratio 0.55, 95% confidence interval 0.22 to 1.35)". Notice especially the wide range for this second result.
Epidemiology
While it is not known precisely where or when the virus originated, analyses in scientific journals have suggested that the H1N1 strain responsible for the current outbreak first evolved in September 2008 and circulated amongst humans for several months before being formally recognised and identified as a novel strain of influenza.Mexico
The virus was first reported in two U.S. children in March 2009, but health officials have reported that it apparently infected people as early as January 2009 in Mexico. The outbreak was first detected in Mexico CityMexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
on 18 March 2009; immediately after the outbreak was officially announced, Mexico notified the U.S. and World Health Organization, and within days of the outbreak Mexico City was "effectively shut down". Some countries cancelled flights to Mexico while others halted trade. Calls to close the border to contain the spread were rejected. Mexico already had hundreds of non-lethal cases before the outbreak was officially discovered, and was therefore in the midst of a "silent epidemic". As a result, Mexico was reporting only the most serious cases which showed more severe signs different from those of normal flu, possibly leading to a skewed initial estimate of the case fatality rate.
United States
The new strain was first identified by the CDC in two children, neither of whom had been in contact with pigs. The first case, from San Diego County, CaliforniaSan Diego County, California
San Diego County is a large county located in the southwestern corner of the US state of California. Hence, San Diego County is also located in the southwestern corner of the 48 contiguous United States. Its county seat and largest city is San Diego. Its population was about 2,813,835 in the 2000...
, was confirmed from clinical specimens (nasopharyngeal
Nasopharynx
The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent .-Lateral:On its lateral wall is the pharyngeal ostium of the...
swab
Cotton swab
Cotton swabs or cotton buds or ear buds consist of a small wad of cotton wrapped around one or both ends of a short rod, usually made of either wood, rolled paper, or plastic...
) examined by the CDC on 14 April 2009. A second case, from nearby Imperial County, California
Imperial County, California
Imperial County is a county located in the Imperial Valley, in the far southeast of the U.S. state of California, bordering both Arizona and Mexico. It is part of the El Centro Metropolitan Area, which encompasses all of Imperial County. The population as of 2000 was 142,361. The county seat is the...
, was confirmed on 17 April. The patient in the first confirmed case had flu symptoms including fever and cough on clinical examination on 30 March, and the second on 28 March.
The first confirmed H1N1/09 pandemic flu death, which occurred at Texas Children's Hospital
Texas Children's Hospital
Texas Children's Hospital is a pediatric hospital located in the Texas Medical Center in Houston, Texas.With 639 licensed beds and 465 beds in operation, Texas Children's is the largest children's hospital in the United States and is affiliated with the Baylor College of Medicine as that...
in Houston, Texas, was of a toddler from Mexico City who was visiting family in Brownsville, Texas
Brownsville, Texas
Brownsville is a city in the southernmost tip of the state of Texas, in the United States. It is located on the northern bank of the Rio Grande, directly north and across the border from Matamoros, Tamaulipas, Mexico. Brownsville is the 16th largest city in the state of Texas with a population of...
, before being air-lifted to Houston for treatment.
Data reporting and accuracy
Influenza surveillance information "answers the questions of where, when, and what influenza viruses are circulating. It can be used to determine if influenza activity is increasing or decreasing, but cannot be used to ascertain how many people have become ill with influenza". For example, as of late June 2009, influenza surveillance information showed the U.S. had nearly 28,000 laboratory-confirmed cases including 3,065 hospitalisations and 127 deaths; but mathematical modelling showed an estimated Americans currently had the 2009 pandemic flu, according to Lyn Finelli, a flu surveillance official with the CDC. Estimating deaths from influenza is also a complicated process. In 2005, influenza only appeared on the death certificates of 1,812 people in the US. The average annual US death toll from flu is, however, estimated to be 36,000. The CDC explains: "[I]nfluenza is infrequently listed on death certificates of people who die from flu-related complications" and hence, "Only counting deaths where influenza was included on a death certificate would be a gross underestimation of influenza's true impact".With respect to the current H1N1 flu pandemic, influenza surveillance information is available but almost no studies have attempted to estimate the total number of deaths attributable to H1N1 flu. Two studies have been performed by the CDC, however; the most recent estimates that there were 9,820 deaths (range 7,070–13,930) attributable to H1N1 flu from April to 14 November 2009. During the same period, 1642 deaths were officially confirmed as caused by H1N1 flu. The WHO state that total mortality (including deaths unconfirmed or unreported) from H1N1 flu is "unquestionably higher" than their own confirmed death statistics.
The initial outbreak received a week of near-constant media attention. Epidemiologists cautioned that the number of cases reported in the early days of an outbreak can be very inaccurate and deceptive due to several causes, among them selection bias
Selection bias
Selection bias is a statistical bias in which there is an error in choosing the individuals or groups to take part in a scientific study. It is sometimes referred to as the selection effect. The term "selection bias" most often refers to the distortion of a statistical analysis, resulting from the...
, media bias
Media bias
Media bias refers to the bias of journalists and news producers within the mass media in the selection of events and stories that are reported and how they are covered. The term "media bias" implies a pervasive or widespread bias contravening the standards of journalism, rather than the...
and incorrect reporting by governments. Inaccuracies could also be caused by authorities in different countries looking at differing population groups. Furthermore, countries with poor health care systems and older laboratory facilities may take longer to identify or report cases. "[E]ven in developed countries the [numbers of flu deaths] are uncertain, because medical authorities don't usually verify who actually died of influenza and who died of a flu-like illness". Dr. Joseph S. Bresee (the CDC flu division's epidemiology chief) and Dr. Michael Osterholm
Michael Osterholm
Michael T. Osterholm, Ph.D., M.P.H., is a prominent public health scientist and a nationally recognized biosecurity expert in the United States. Osterholm is the director of the Center for Infectious Disease Research and Policy at the University of Minnesota, a professor in the School of Public...
(director of the Center for Infectious Disease Research and Policy
Center for Infectious Disease Research and Policy
The Center for Infectious Disease Research and Policy is a center within the University of Minnesota that focuses on addressing public health preparedness and emerging infectious disease response...
) have pointed out that millions of people have had H1N1 flu, usually in a mild form, so the numbers of laboratory-confirmed cases were actually meaningless, and in July 2009 the WHO stopped keeping count of individual cases and focused more on major outbreaks.
Followup
A Wisconsin study published in the Journal of the American Medical AssociationJournal of the American Medical Association
The Journal of the American Medical Association is a weekly, peer-reviewed, medical journal, published by the American Medical Association. Beginning in July 2011, the editor in chief will be Howard C. Bauchner, vice chairman of pediatrics at Boston University’s School of Medicine, replacing ...
in September 2010, reported that findings showed that the 2009 H1N1 flu was no more severe than the seasonal flu. "The risk of most serious complications was not elevated in adults or children", the study's authors wrote. "Children were disproportionately affected by 2009 H1N1 infection, but the perceived severity of symptoms and risk of serious outcomes were not increased." Children infected in the 2009 H1N1 flu pandemic were no more likely to be hospitalized with complications or get pneumonia than those who catch seasonal strains. About 1.5% of children with the H1N1 swine flu strain were hospitalized within 30 days, compared with 3.7% of those sick with a seasonal strain of H1N1 and 3.1% with an H3N2 virus.
CDC illness and death estimates from April 2009 to April 2010, are as follows:
- CDC estimates that between 43 million and 89 million cases of 2009 H1N1 occurred between April 2009 and 10 April 2010. The mid-level in this range is about 61 million people infected with 2009 H1N1.
- CDC estimates that between about 195,000 and 403,000 H1N1-related hospitalizations occurred between April 2009 and 10 April 2010. The mid-level in this range is about 274,000 2009 H1N1-related hospitalizations.
- CDC estimates that between about 8,870 and 18,300 2009 H1N1-related deaths occurred between April 2009 and 10 April 2010. The mid-level in this range is about 12,470 2009 H1N1-related deaths.
It is often stated that about 36,000 die from the seasonal flu in the U.S. each year, and this is frequently understood as an indication that the H1N1 strain was not as severe as seasonal influenza. The 36,000 estimate was presented in a 2003 study by CDC scientists published in the Journal of the American Medical Association but only refers to a period from 1990-91 through 1998-99. During those years, the number of estimated deaths ranged from 17,000 to 52,000, with an average of about 36,000. The JAMA study also looked at seasonal influenza-associated deaths over a 23 year period, from 1976-1977 and 1998-1999. During that period, estimates of respiratory and circulatory influenza-associated deaths ranged from about 5,000 to about 52,000, with an average of about 25,000. While the 36,000 number is often cited, it's important to note that during that decade, influenza A (H3N2) was the predominant virus during most of the seasons, and H3N2 influenza viruses are typically associated with higher death rates. CDC believes that the range of deaths over the past 31 years (~3,000 to ~49,000) is a more accurate representation of the unpredictability and variability of flu-associated deaths. The annual toll from seasonal influenza in the US is more accurately estimated at 3000-49,000 deaths per year. So the H1N1 pandemic estimated mortality of 8,870 to 18,300, places it in the mid-range of estimates.
The 2009 pandemic caused hospitals around the country to make significant preparations in terms of hospital surge capacities, especially within the emergency department and among vulnerable populations. In many cases, hospitals were relatively successful in making sure that those patients most severely affected by the influenza strain were able to be seen, treated, and discharged in an efficient manner. A proper case-study of the preparation, planning, mitigation, and response efforts during the Fall of 2009 is that of the Children's Hospital of Philadelphia (CHOP). For example, CHOP took several steps to increase the emergency department (ED) surge capacity response abilities through careful planning and mitigation efforts. To increase ED capacity and response, CHOP used portions of the main lobby area as an ED waiting room; several of the region's hospital-based outpatient facilities were in use during evening and weekend hours for non-emergent cases; the ED's 24-hour short-stay unit was utilized to care for ED patients in a longer-term capacity; non-board certified physicians (in pediatric emergency medicine) and inpatient-unit medical nurses were utilized for ED patient care; hospital units normally utilized for other medical or therapeutic purposes were transformed into ED patient rooms; and rooms normally used for only one patient were expanded to at least a capacity of 2
Comparisons to other pandemics and epidemics
Annual influenza epidemics are estimated to affect 5–15% of the global population. Although most cases are mild, these epidemics still cause severe illness in people and 250,000–500,000 deaths worldwide. On average 41,400 people die of influenza-related illnesses each year in the United States, based on data collected between 1979 and 2001. In industrialised countries, severe illness and deaths occur mainly in the high-risk populations of infants, the elderly and chronically ill patients, although the H1N1 flu outbreak (like the 1918 Spanish fluSpanish flu
The 1918 flu pandemic was an influenza pandemic, and the first of the two pandemics involving H1N1 influenza virus . It was an unusually severe and deadly pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin...
) differs in its tendency to affect younger, healthier people.
In addition to these annual epidemics, Influenza A virus strains caused three global pandemics during the 20th century: the Spanish flu in 1918, Asian flu
Asian flu
Asian Flu may refer to:* The Asian Financial Crisis of 1997, or* Asian Flu, the H2N2 virus...
in 1957, and Hong Kong flu
Hong Kong flu
The Hong Kong flu was a category 2 flu pandemic whose outbreak in 1968 and 1969 killed an estimated one million people worldwide. It was caused by an H3N2 strain of the influenza A virus, descended from H2N2 through antigenic shift, a genetic process in which genes from multiple subtypes reassorted...
in 1968–69. These virus strains had undergone major genetic changes
Antigenic shift
Antigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains...
for which the population did not possess significant immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
. Recent genetic analysis has revealed that three-quarters, or six out of the eight genetic segments, of the 2009 flu pandemic strain arose from the North American swine flu strains circulating since 1998, when a new strain was first identified on a factory farm in North Carolina, and which was the first-ever reported triple-hybrid flu virus.
The 1918 flu epidemic began with a wave of mild cases in the spring, followed by more deadly waves in the autumn, eventually killing hundreds of thousands in the United States. The great majority of deaths in the 1918 flu pandemic were the result of secondary bacterial pneumonia. The influenza virus damaged the lining of the bronchial tubes and lungs of victims, allowing common bacteria from the nose and throat to infect their lungs. Subsequent pandemics have had many fewer fatalities due to the development of antibiotic medicines which can treat pneumonia.
| Pandemic | Year | Influenza virus Orthomyxoviridae The Orthomyxoviridae are a family of RNA viruses that includes five genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus and Thogotovirus. A sixth has recently been described... type |
People infected (approximate) | Estimated deaths worldwide | Case fatality rate |
|---|---|---|---|---|---|
| Spanish flu | 1918–1919 | A/H1N1 | 33% (500 million) | 20–100 million | >2.5% |
| Asian flu Asian flu Asian Flu may refer to:* The Asian Financial Crisis of 1997, or* Asian Flu, the H2N2 virus... |
1956–1958 | A/H2N2 | 2 million | <0.1% | |
| Hong Kong flu Hong Kong flu The Hong Kong flu was a category 2 flu pandemic whose outbreak in 1968 and 1969 killed an estimated one million people worldwide. It was caused by an H3N2 strain of the influenza A virus, descended from H2N2 through antigenic shift, a genetic process in which genes from multiple subtypes reassorted... |
1968–1969 | A/H3N2 | 1 million | <0.1% | |
| Seasonal flu Flu season Flu season is a annually-recurring time period characterized by the prevalence of outbreaks of influenza . The season occurs during the cold half of the year in each hemisphere. Influenza activity can sometimes be predicted and even tracked geographically... Not necessarily pandemic, but included for comparison purposes. |
Every year | mainly A/H3N2, A/H1N1, and B Influenzavirus B Influenzavirus B is a genus in the virus family Orthomyxoviridae. The only species in this genus is called "Influenza B virus".Influenza B viruses are only known to infect humans and seals, giving them influenza... |
5–15% (340 million – 1 billion) | 250,000–500,000 per year | <0.1% |
| Swine flu | 2009–2010 | Pandemic H1N1/09 Pandemic H1N1/09 virus The Pandemic H1N1/09 virus is a swine origin Influenza A virus subtype H1N1 virus strain responsible for the 2009 flu pandemic. For other names see the Nomenclature section below.-Virus characteristics:... |
> 622,482 (lab-confirmed) | (lab-confirmed; ECDC) 18,036 (lab-confirmed; WHO) |
0.03% |
The influenza virus has also caused several pandemic threats over the past century, including the pseudo-pandemic of 1947 (thought of as mild because although globally distributed, it caused relatively few deaths), the 1976 swine flu outbreak
1976 swine flu outbreak
The 1976 swine flu outbreak, also known as the swine flu fiasco, or the swine flu debacle, was a strain of H1N1 influenza virus that appeared in 1976. Infections were only detected from January 19 to February 9, and were not found outside Fort Dix. The outbreak is most remembered for the mass...
and the 1977 Russian flu, all caused by the H1N1 subtype. The world has been at an increased level of alert since the SARS
Severe acute respiratory syndrome
Severe Acute Respiratory Syndrome is a respiratory disease in humans which is caused by the SARS coronavirus . Between November 2002 and July 2003 an outbreak of SARS in Hong Kong nearly became a pandemic, with 8,422 cases and 916 deaths worldwide according to the WHO...
epidemic in Southeast Asia (caused by the SARS coronavirus
SARS coronavirus
The SARS coronavirus, sometimes shortened to SARS-CoV, is the virus that causes severe acute respiratory syndrome . On April 16, 2003, following the outbreak of SARS in Asia and secondary cases elsewhere in the world, the World Health Organization issued a press release stating that the...
). The level of preparedness was further increased and sustained with the advent of the H5N1 bird flu outbreaks because of H5N1's high fatality rate, although the strains currently prevalent have limited human-to-human transmission (anthroponotic) capability, or epidemicity.
People who contracted flu before 1957 appeared to have some immunity to H1N1 flu. Dr. Daniel Jernigan, head of flu epidemiology for the U.S. CDC, has stated: "Tests on blood serum
Blood serum
In blood, the serum is the component that is neither a blood cell nor a clotting factor; it is the blood plasma with the fibrinogens removed...
from older people showed that they had antibodies that attacked the new virus ... That does not mean that everyone over 52 is immune, since Americans and Mexicans older than that have died of the new flu".
External links
- Pandemic (H1N1) 2009 at the World Health OrganizationWorld Health OrganizationThe World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) - International Society for Infectious Diseases PROMED-mail news updates
- H1N1 Flu Resource Centre of The LancetThe LancetThe Lancet is a weekly peer-reviewed general medical journal. It is one of the world's best known, oldest, and most respected general medical journals...
- Influenza Research Database – Database of influenza genomic sequences and related information.
- CDC 2009 H1N1 Influenza Vaccine Supply Status
- The H1N1 Pandemic and Global Health Security, Dean Julio Frenk, 2009-09-17
Europe
- Health-EU Portal EU response to influenza
- 2009 influenza A (H1N1) pandemic. European Centre for Disease Prevention and ControlEuropean Centre for Disease Prevention and ControlThe European Centre for Disease Prevention and Control is an independent agency of the European Union aimed at strengthening Europe's defences against infectious diseases. It was established in 2005 and is located in Solna, Sweden....
(ECDC). - Summaries of the pandemic. European Centre for Disease Prevention and ControlEuropean Centre for Disease Prevention and ControlThe European Centre for Disease Prevention and Control is an independent agency of the European Union aimed at strengthening Europe's defences against infectious diseases. It was established in 2005 and is located in Solna, Sweden....
(ECDC). - European Commission – Public Health EU coordination on Pandemic (H1N1) 2009.
- UK National Pandemic Flu Service
- Official UK government information on swine flu from DirectgovDirectgovDirectgov is the UK government's digital service for people in the United Kingdom, providing a single point of access to public sector information and services.The content is developed by government departments, working with a central Directgov team...
- Human/Swine A/H1N1 Influenza Origins and Evolution – Analysis of genetic data for the origin and evolution of swine flu virus.
North America
- Health Canada flu portal
- Pan-American Health Organization (PAHO) Swine Influenza portal
- H1N1 Influenza (Flu) portal at the US Centers for Disease Control (CDC)
- US Government swine, avian and pandemic flu portal
- Medical Encyclopedia Medline Plus: Swine Flu
- Swine Flu Outbreak, Influenza Virus Resource – Sequences and related resources (GenBank, NCBI)