H3N2
Encyclopedia
Influenza A virus subtype H3N2 (also H3N2) is a subtype of virus
es that cause influenza
(flu). H3N2 Virus
es can infect birds and mammals. In birds, humans, and pig
s, the virus has mutated
into many strains. H3N2 is increasingly abundant in seasonal influenza, which kills an estimated 36,000 people in the United States each year.
Influenzavirus A
, which is an important cause of human influenza. Its name derives from the forms of the two kinds of protein
s on the surface of its coat, hemagglutinin
(H) and neuraminidase
(N). By reassortment
, H3N2 exchanges genes for internal proteins with other influenza subtypes.
, H3N2, H1N2
, and influenza B
will proliferate in the next season. Separate vaccines are developed for the northern and southern hemispheres in preparation for their annual epidemics. In the tropics, influenza shows no clear seasonality. In the past ten years, H3N2 has tended to dominate in prevalence over H1N1, H1N2, and influenza B. Measured resistance to the standard antiviral drugs amantadine
and rimantadine
in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005.
Seasonal H3N2 flu is a human flu from H3N2 that is slightly different from one of last year's flu season
H3N2 variants. Seasonal influenza viruses flow out of overlapping epidemics in East and Southeast Asia
, then trickle around the globe before dying off. Identifying the source of the viruses allows global health officials to better predict which viruses are most likely to cause the most disease over the next year. An analysis of 13,000 samples of influenza A/H3N2 virus that were collected across six continents from 2002 to 2007 by the WHO's Global Influenza Surveillance Network showed that newly emerging strains of H3N2 appeared in East and Southeast Asian countries about 6 to 9 months earlier than anywhere else. The strains generally reached Australia
and New Zealand
next, followed by North America
and Europe. The new variants typically reached South America after an additional 6 to 9 months, the group reported.
"In swine, 3 influenza A virus subtypes (H1N1
, H3N2, and H1N2
) are circulating throughout the world. In the United States, the classic H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. Most H3N2 virus isolates are triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages. [...] Present vaccination strategies for SIV control and prevention in swine farms typically include the use of 1 of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactions with antiserum to 3 commercial SIV vaccines. Since the protective ability of influenza vaccines depends primarily on the closeness of the match between the vaccine virus and the epidemic virus, the presence of nonreactive H3N2 SIV variants suggests that current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses."
Avian influenza virus H3N2
is endemic in pig
s in China
and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains. Health experts say pigs can carry human influenza
viruses, which can combine (i.e. exchange homologous genome sub-units by genetic reassortment
) with H5N1
, passing gene
s and mutating into a form which can pass easily among humans. H3N2 evolved from H2N2
by antigenic shift
and caused the Hong Kong Flu
pandemic of 1968 and 1969 that killed up to 750,000 humans. The dominant strain of annual flu in humans in January 2006 is H3N2
. Measured resistance to the standard antiviral drugs amantadine
and rimantadine
in H3N2 in humans has increased to 91% in 2005. In August 2004, researchers in China found H5N1 in pigs.
11/10/2010 The Centers for Disease Control and Prevention (CDC) has issued the following alert: Influenza A (H3N2) virus infections have been recently detected in people in a number of states across the U.S., including two small localized outbreaks. Sporadic cases of influenza and localized summer outbreaks from seasonal influenza viruses are detected each summer.
The Hong Kong Flu was a category 2
flu pandemic caused by a strain of H3N2 descended from H2N2
by antigenic shift
, in which genes from multiple subtypes reassorted to form a new virus. This pandemic of 1968 and 1969 killed an estimated one million people worldwide. The pandemic infected an estimated 500,000 Hong Kong residents, 15% of the population, with a low death rate.
In the United States, approximately 33,800 people died.
Both the H2N2
and H3N2 pandemic flu strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible. H1N1 may have been transmitted directly from birds to humans (Belshe 2005).
The Hong Kong flu strain shared internal genes and the neuraminidase
with the 1957 Asian Flu
(H2N2
). Accumulated antibodies to the neuraminidase or internal proteins may have resulted in much fewer casualties than most pandemic
s. However, cross-immunity within and between subtypes of influenza is poorly understood.
The Hong Kong flu was the first known outbreak of the H3N2 strain, though there is serologic evidence of H3N? infections in the late 19th century. The first record of the outbreak in Hong Kong appeared on 13 July 1968 in an area with a density of about 500 people per acre in an urban setting. The outbreak reached maximum intensity in 2 weeks, lasting 6 weeks in total. The virus was isolated in Queen Mary Hospital
. Flu symptoms lasted 4 to 5 days.
By July 1968, extensive outbreaks were reported in Vietnam
and Singapore
. By September 1968, it reached India
, Philippines
, northern Australia
and Europe. That same month, the virus entered California
from returning Vietnam War
troops. It would reach Japan
, Africa and South America by 1969.
"Three strains of Hong Kong influenza virus isolated from humans were compared with a strain isolated from a calf for their ability to cause disease in calves. One of the human strains. A/Aichi/2/68, was detected for five days in a calf, but all three failed to cause signs of disease. Strain A/cal/Duschanbe/55/71 could be detected for seven days and caused an influenza-like illness in calves."
Fujian flu refers to flu caused by either a Fujian human flu
strain of the H3N2
subtype of the Influenza A virus
or a Fujian bird flu strain of the H5N1
subtype of the Influenza A virus. These strains are named after Fujian
, a coastal province of the People's Republic of China
that is across the Taiwan strait
from Taiwan
.
A/Fujian (H3N2) human flu (from A/Fujian/411/2002(H3N2) -like flu virus strains) caused an unusually severe 2003–2004 flu season. This was due to a reassortment
event that caused a minor clade to provide a haemagglutinin gene that later became part of the dominant strain in the 2002–2003 flu season. A/Fujian (H3N2) was made part of the trivalent influenza vaccine for the 2004–2005 flu season
and its descendants are still the most common human H3N2 strain.
, and B/Shanghai/361/2002-like viruses.
s produced for the 2005–2006 season use:
"A/H3N2 has become the predominant flu subtype in the United States, and the record over the past 25 years shows that seasons dominated by H3N2 tend to be worse than those dominated by type A/H1N1 or type B." Many H3N2 viruses making people ill in this 2007–2008 flu season differ from the strains in the vaccine and may not be well covered by the vaccine strains. "The CDC has analyzed 250 viruses this season to determine how well they match up with the vaccine, the report says. Of 65 H3N2 isolates, 53 (81%) were characterized as A/Brisbane/10/2007-like, a variant that has evolved [notably] from the H3N2 strain in the vaccine—A/Wisconsin/67/2005."
As of May 30, 2009: "CDC has antigenically characterized 1,567 seasonal human influenza viruses [947 influenza A (H1), 162 influenza A (H3) and 458 influenza B viruses] collected by U.S. laboratories since October 1, 2008, and 84 novel influenza A (H1N1) viruses. All 947 influenza seasonal A (H1) viruses are related to the influenza A (H1N1) component of the 2008-09 influenza vaccine (A/Brisbane/59/2007). All 162 influenza A (H3N2) viruses are related to the A (H3N2) vaccine component (A/Brisbane/10/2007). All 84 novel influenza A (H1N1) viruses are related to the A/California/07/2009 (H1N1) reference virus selected by WHO as a potential candidate for novel influenza A (H1N1) vaccine. Influenza B viruses currently circulating can be divided into two distinct lineages represented by the B/Yamagata/16/88 and B/Victoria/02/87 viruses. Sixty-one influenza B viruses tested belong to the B/Yamagata lineage and are related to the vaccine strain (B/Florida/04/2006). The remaining 397 viruses belong to the B/Victoria lineage and are not related to the vaccine strain."
s produced for the 2009–2010 season use:
There also was also a separate vaccine available for Pandemic H1N1 Influenza using the A/California/7/2009-like Pandemic H1N1 Strain.
s produced for the 2010–2011 season use:
s produced for the 2011–2012 season use:
Note: 2011-2012 Influenza Vaccine Composition
The viruses used in making seasonal flu vaccines are chosen each year based on information collected over the previous year
about which influenza viruses are spreading and what vaccine viruses would offer the best protection against circulating
viruses. Viruses gathered by 136 national influenza centers in 106 countries as well as information on disease trends are
further analyzed by the five World Health Organization (WHO) Collaborating Centers for Reference and Research on
Influenza located in Atlanta, Georgia, USA (Centers for Disease Control and Prevention, CDC); London, United Kingdom
(National Institute for Medical Research); Melbourne, Australia (Victoria Infectious Diseases Reference Laboratory); Tokyo,
Japan (National Institute for Infectious Diseases); and Beijing, China (National Institute for Viral Disease Control and
Prevention).
The seasonal flu vaccine is usually a trivalent vaccine (a three component vaccine) with each component selected to protect
against one of the three groups of influenza viruses circulating most commonly in humans. The 2009 H1N1 vaccine that
was made to protect against the pandemic virus first detected in April, 2009 was a monovalent (one-component) vaccine
that only protects against the 2009 H1N1 virus.
The three vaccine viruses are chosen to maximize the likelihood that the main circulating viruses during the upcoming flu
season will be well covered. WHO recommends specific vaccine viruses for vaccine production, but then each individual
country makes their own decision for licensing of vaccines in their country. In the United States, the US Food and Drug
Administration (FDA) determines what viruses will be used in US–licensed vaccines.
WHO recommended that the Northern Hemisphere’s 2011-2012 seasonal influenza vaccine contain the following three
vaccine viruses:
These are the same viruses that were selected for the Northern Hemisphere for the 2010-2011 influenza vaccine. This
recommended composition of the seasonal vaccine for the Northern Hemisphere, including the United States, is the
same composition that was recommended for the Southern Hemisphere’s 2011-2012 influenza vaccines.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es that cause influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
(flu). H3N2 Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es can infect birds and mammals. In birds, humans, and pig
Pig
A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives...
s, the virus has mutated
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
into many strains. H3N2 is increasingly abundant in seasonal influenza, which kills an estimated 36,000 people in the United States each year.
Classification
H3N2 is a subtype of the viral genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Influenzavirus A
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
, which is an important cause of human influenza. Its name derives from the forms of the two kinds of 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 on the surface of its coat, hemagglutinin
Hemagglutinin
Influenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...
(H) and neuraminidase
Neuraminidase
Neuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...
(N). By 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...
, H3N2 exchanges genes for internal proteins with other influenza subtypes.
Seasonal H3N2 flu
Seasonal influenza kills an estimated 36,000 people in the United States each year. Flu vaccines are based on predicting which mutants of H1N1H1N1
'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
, H3N2, H1N2
H1N2
H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
, and influenza 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...
will proliferate in the next season. Separate vaccines are developed for the northern and southern hemispheres in preparation for their annual epidemics. In the tropics, influenza shows no clear seasonality. In the past ten years, H3N2 has tended to dominate in prevalence over H1N1, H1N2, and influenza B. Measured resistance to the standard antiviral drugs amantadine
Amantadine
Amantadine is the organic compound known formally as 1-adamantylamine or 1-aminoadamantane. The molecule consists of adamantane backbone that has an amino group substituted at one of the four methyne positions. This pharmaceutical is sold under the name Symmetrel for use both as an antiviral and an...
and rimantadine
Rimantadine
Rimantadine is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Both rimantadine and the similar drug...
in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005.
Seasonal H3N2 flu is a human flu from H3N2 that is slightly different from one of last year's flu season
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...
H3N2 variants. Seasonal influenza viruses flow out of overlapping epidemics in East and Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, then trickle around the globe before dying off. Identifying the source of the viruses allows global health officials to better predict which viruses are most likely to cause the most disease over the next year. An analysis of 13,000 samples of influenza A/H3N2 virus that were collected across six continents from 2002 to 2007 by the WHO's Global Influenza Surveillance Network showed that newly emerging strains of H3N2 appeared in East and Southeast Asian countries about 6 to 9 months earlier than anywhere else. The strains generally reached Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
next, followed by North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Europe. The new variants typically reached South America after an additional 6 to 9 months, the group reported.
Swine flu
H1N1
'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
, H3N2, and H1N2
H1N2
H1N2 is a subtype of the species Influenza A virus . It is currently pandemic in both human and pig populations.H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans....
) are circulating throughout the world. In the United States, the classic H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. Most H3N2 virus isolates are triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages. [...] Present vaccination strategies for SIV control and prevention in swine farms typically include the use of 1 of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactions with antiserum to 3 commercial SIV vaccines. Since the protective ability of influenza vaccines depends primarily on the closeness of the match between the vaccine virus and the epidemic virus, the presence of nonreactive H3N2 SIV variants suggests that current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses."
Avian influenza virus H3N2
H3N2
Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
is endemic in pig
Pig
A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives...
s in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains. Health experts say pigs can carry human influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
viruses, which can combine (i.e. exchange homologous genome sub-units by genetic 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...
) with 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...
, passing gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s and mutating into a form which can pass easily among humans. H3N2 evolved from H2N2
H2N2
H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
by antigenic shift
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...
and caused the 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...
pandemic of 1968 and 1969 that killed up to 750,000 humans. The dominant strain of annual flu in humans in January 2006 is H3N2
H3N2
Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
. Measured resistance to the standard antiviral drugs amantadine
Amantadine
Amantadine is the organic compound known formally as 1-adamantylamine or 1-aminoadamantane. The molecule consists of adamantane backbone that has an amino group substituted at one of the four methyne positions. This pharmaceutical is sold under the name Symmetrel for use both as an antiviral and an...
and rimantadine
Rimantadine
Rimantadine is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Both rimantadine and the similar drug...
in H3N2 in humans has increased to 91% in 2005. In August 2004, researchers in China found H5N1 in pigs.
11/10/2010 The Centers for Disease Control and Prevention (CDC) has issued the following alert: Influenza A (H3N2) virus infections have been recently detected in people in a number of states across the U.S., including two small localized outbreaks. Sporadic cases of influenza and localized summer outbreaks from seasonal influenza viruses are detected each summer.
Hong Kong Flu (1968–1969)
Pandemic Severity Index
The Pandemic Severity Index is a proposed classification scale for reporting the severity of influenza pandemics in the United States. The PSI was accompanied by a set of guidelines intended to help communicate appropriate actions for communities to follow in potential pandemic situations...
flu pandemic caused by a strain of H3N2 descended from H2N2
H2N2
H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
by antigenic shift
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...
, in which genes from multiple subtypes reassorted to form a new virus. This pandemic of 1968 and 1969 killed an estimated one million people worldwide. The pandemic infected an estimated 500,000 Hong Kong residents, 15% of the population, with a low death rate.
In the United States, approximately 33,800 people died.
Both the H2N2
H2N2
H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
and H3N2 pandemic flu strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible. H1N1 may have been transmitted directly from birds to humans (Belshe 2005).
The Hong Kong flu strain shared internal genes and the neuraminidase
Neuraminidase
Neuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...
with the 1957 Asian Flu
Asian flu
Asian Flu may refer to:* The Asian Financial Crisis of 1997, or* Asian Flu, the H2N2 virus...
(H2N2
H2N2
H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...
). Accumulated antibodies to the neuraminidase or internal proteins may have resulted in much fewer casualties than most 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...
s. However, cross-immunity within and between subtypes of influenza is poorly understood.
The Hong Kong flu was the first known outbreak of the H3N2 strain, though there is serologic evidence of H3N? infections in the late 19th century. The first record of the outbreak in Hong Kong appeared on 13 July 1968 in an area with a density of about 500 people per acre in an urban setting. The outbreak reached maximum intensity in 2 weeks, lasting 6 weeks in total. The virus was isolated in Queen Mary Hospital
Queen Mary Hospital, Hong Kong
Queen Mary Hospital , located in Pok Fu Lam on Hong Kong Island of Hong Kong, is the flagship teaching hospital of the Faculty of Dentistry and Li Ka Shing Faculty of Medicine of the University of Hong Kong...
. Flu symptoms lasted 4 to 5 days.
By July 1968, extensive outbreaks were reported in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
and Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
. By September 1968, it reached India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Europe. That same month, the virus entered California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
from returning Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
troops. It would reach Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, Africa and South America by 1969.
"Three strains of Hong Kong influenza virus isolated from humans were compared with a strain isolated from a calf for their ability to cause disease in calves. One of the human strains. A/Aichi/2/68, was detected for five days in a calf, but all three failed to cause signs of disease. Strain A/cal/Duschanbe/55/71 could be detected for seven days and caused an influenza-like illness in calves."
Fujian flu (2003–2004)
Human flu
Human flu is a term used to refer to influenza cases caused by Orthomyxoviridae that are endemic to human populations . It is an arbitrary categorization scheme, and is not associated with phylogenetics-based taxonomy...
strain of the H3N2
H3N2
Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
subtype of the Influenza A virus
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...
or a Fujian bird flu strain of the 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...
subtype of the Influenza A virus. These strains are named after Fujian
Fujian
' , formerly romanised as Fukien or Huguing or Foukien, is a province on the southeast coast of mainland China. Fujian is bordered by Zhejiang to the north, Jiangxi to the west, and Guangdong to the south. Taiwan lies to the east, across the Taiwan Strait...
, a coastal province of the People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
that is across the Taiwan strait
Taiwan Strait
The Taiwan Strait or Formosa Strait, formerly known as the Black Ditch, is a 180-km-wide strait separating Mainland China and Taiwan. The strait is part of the South China Sea and connects to East China Sea to the northeast...
from 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...
.
A/Fujian (H3N2) human flu (from A/Fujian/411/2002(H3N2) -like flu virus strains) caused an unusually severe 2003–2004 flu season. This was due to a 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...
event that caused a minor clade to provide a haemagglutinin gene that later became part of the dominant strain in the 2002–2003 flu season. A/Fujian (H3N2) was made part of the trivalent influenza vaccine for the 2004–2005 flu season
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...
and its descendants are still the most common human H3N2 strain.
2004–2005 flu season
The 2004–05 trivalent influenza vaccine for the United States contained A/New Caledonia/20/99-like (H1N1), A/Fujian/411/2002-like (H3N2)Fujian flu
Fujian flu refers to flu caused by either a Fujian human flu strain of the H3N2 subtype of the Influenza A virus or a Fujian bird flu strain of the H5N1 subtype of the Influenza A virus...
, and B/Shanghai/361/2002-like viruses.
2005–2006 flu season
The vaccineVaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s produced for the 2005–2006 season use:
- an A/New Caledonia/20/1999-like(H1N1H1N1'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of...
); - an A/California/7/2004-like(H3N2H3N2Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...
) (or the antigenically equivalent strain A/New York/55/2004); - a B/Jiangsu/10/2003-like viruses.
2006–2007 flu season
The 2006–2007 influenza vaccine composition recommended by the World Health Organization on 15 February 2006 and the U.S. FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) on 17 February 2006 use:- an A/New Caledonia/20/99 (H1N1)-like virus;
- an A/Wisconsin/67/2005 (H3N2)-like virus (A/Wisconsin/67/2005 and A/Hiroshima/52/2005 strains);
- a B/Malaysia/2506/2004-like virus from B/Malaysia/2506/2004 and B/Ohio/1/2005 strains which are of B/Victoria/2/87 lineage.
2007–2008 flu season
The composition of influenza virus vaccines for use in the 2007–2008 Northern Hemisphere influenza season recommended by the World Health Organization on 14 February 2007 was:- an A/Solomon Islands/3/2006 (H1N1)-like virus;
- an A/Wisconsin/67/2005 (H3N2)-like virus (A/Wisconsin/67/2005 (H3N2) and A/Hiroshima/52/2005 were used at the time);
- a B/Malaysia/2506/2004-like virus
"A/H3N2 has become the predominant flu subtype in the United States, and the record over the past 25 years shows that seasons dominated by H3N2 tend to be worse than those dominated by type A/H1N1 or type B." Many H3N2 viruses making people ill in this 2007–2008 flu season differ from the strains in the vaccine and may not be well covered by the vaccine strains. "The CDC has analyzed 250 viruses this season to determine how well they match up with the vaccine, the report says. Of 65 H3N2 isolates, 53 (81%) were characterized as A/Brisbane/10/2007-like, a variant that has evolved [notably] from the H3N2 strain in the vaccine—A/Wisconsin/67/2005."
2008-2009 flu season
The composition of virus vaccines for use in the 2008-2009 Northern Hemisphere influenza season recommended by the World Health Organization on February 14, 2008 was:- an A/Brisbane/59/2007 (H1N1)-like virus;
- an A/Brisbane/10/2007 (H3N2)-like virus;
- a B/Florida/4/2006-like virus (B/Florida/4/2006 and B/Brisbane/3/2007 (a B/Florida/4/2006-like virus) were used at the time).
As of May 30, 2009: "CDC has antigenically characterized 1,567 seasonal human influenza viruses [947 influenza A (H1), 162 influenza A (H3) and 458 influenza B viruses] collected by U.S. laboratories since October 1, 2008, and 84 novel influenza A (H1N1) viruses. All 947 influenza seasonal A (H1) viruses are related to the influenza A (H1N1) component of the 2008-09 influenza vaccine (A/Brisbane/59/2007). All 162 influenza A (H3N2) viruses are related to the A (H3N2) vaccine component (A/Brisbane/10/2007). All 84 novel influenza A (H1N1) viruses are related to the A/California/07/2009 (H1N1) reference virus selected by WHO as a potential candidate for novel influenza A (H1N1) vaccine. Influenza B viruses currently circulating can be divided into two distinct lineages represented by the B/Yamagata/16/88 and B/Victoria/02/87 viruses. Sixty-one influenza B viruses tested belong to the B/Yamagata lineage and are related to the vaccine strain (B/Florida/04/2006). The remaining 397 viruses belong to the B/Victoria lineage and are not related to the vaccine strain."
2009-2010 flu season
The vaccineVaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s produced for the 2009–2010 season use:
- an A/Brisbane/59/2007(H1N1)-like virus;
- an A/Brisbane/10/2007 (H3N2)-like virus;
- a B/Brisbane 60/2008-like antigens.
There also was also a separate vaccine available for Pandemic H1N1 Influenza using the A/California/7/2009-like Pandemic H1N1 Strain.
2010-2011 flu season
The vaccineVaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s produced for the 2010–2011 season use:
- an A/California/7/2009-like (Pandemic H1N1)
- an A/Perth/16/2009-like (H3N2)-like virus;
- a B/Brisbane/60/2008-like antigens.
2011-2012 flu season
The vaccineVaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s produced for the 2011–2012 season use:
- an A/California/07/2009 (H1N1)-like virus,
- an A/Victoria/210/2009 (an A/Perth/16/2009-like strain) (H3N2)-like virus,
- a B/Brisbane/60/2008-like virus.
Note: 2011-2012 Influenza Vaccine Composition
The viruses used in making seasonal flu vaccines are chosen each year based on information collected over the previous year
about which influenza viruses are spreading and what vaccine viruses would offer the best protection against circulating
viruses. Viruses gathered by 136 national influenza centers in 106 countries as well as information on disease trends are
further analyzed by the five World Health Organization (WHO) Collaborating Centers for Reference and Research on
Influenza located in Atlanta, Georgia, USA (Centers for Disease Control and Prevention, CDC); London, United Kingdom
(National Institute for Medical Research); Melbourne, Australia (Victoria Infectious Diseases Reference Laboratory); Tokyo,
Japan (National Institute for Infectious Diseases); and Beijing, China (National Institute for Viral Disease Control and
Prevention).
The seasonal flu vaccine is usually a trivalent vaccine (a three component vaccine) with each component selected to protect
against one of the three groups of influenza viruses circulating most commonly in humans. The 2009 H1N1 vaccine that
was made to protect against the pandemic virus first detected in April, 2009 was a monovalent (one-component) vaccine
that only protects against the 2009 H1N1 virus.
The three vaccine viruses are chosen to maximize the likelihood that the main circulating viruses during the upcoming flu
season will be well covered. WHO recommends specific vaccine viruses for vaccine production, but then each individual
country makes their own decision for licensing of vaccines in their country. In the United States, the US Food and Drug
Administration (FDA) determines what viruses will be used in US–licensed vaccines.
WHO recommended that the Northern Hemisphere’s 2011-2012 seasonal influenza vaccine contain the following three
vaccine viruses:
- an A/California/7/2009 (H1N1)–like virus,
- an A/Perth/16/2009 (H3N2)–like virus, and
- a B/Brisbane/60/2008–like virus
These are the same viruses that were selected for the Northern Hemisphere for the 2010-2011 influenza vaccine. This
recommended composition of the seasonal vaccine for the Northern Hemisphere, including the United States, is the
same composition that was recommended for the Southern Hemisphere’s 2011-2012 influenza vaccines.
See also
- 2009 H1N1 influenza outbreak
- Bird flu
- Dog flu
- Horse fluHorse fluEquine influenza is the disease caused by strains of Influenza A that are enzootic in horse species. Equine influenza occurs globally, and is caused by two main strains of virus: equine-1 and equine-2...
- Human fluHuman fluHuman flu is a term used to refer to influenza cases caused by Orthomyxoviridae that are endemic to human populations . It is an arbitrary categorization scheme, and is not associated with phylogenetics-based taxonomy...
- Swine fluSwine fluSwine 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...
Further reading
- Graphic showing H3N2 mutations, amino acid by amino acid, among 207 isolates completely sequenced by the Influenza Genome Sequencing ProjectInfluenza Genome Sequencing ProjectThe Influenza Genome Sequencing Project is an American-based genome project aimed at improving the availability of genomic sequence data from influenza viruses and related information....
. - Influenza A (H3N2) Outbreak, Nepal
- Hot topic - Fujian-like strain A influenza
- Monitoring Antibodies for Swine Influenza H3N2 Virus
- New Scientist: Bird Flu
External links
- Influenza Research Database Database of influenza sequences and related information.