Lábrea fever, also known as Lábrea's black fever and Lábrea hepatitis, is a lethal tropical

Tropical disease

Tropical diseases are diseases that are prevalent in or unique to tropical and subtropical regions. The diseases are less prevalent in temperate climates, due in part to the occurrence of a cold season, which controls the insect population by forcing hibernation. Insects such as mosquitoes and...

 viral infection

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...

 discovered in the 1950s in the city of Lábrea

Lábrea

Lábrea is the southernmost municipality in the Brazilian state of Amazonas. Its population is 38,451 and its area is 68.508,6 km². The town is the seat of the Territorial Prelature of Lábrea....

, in the Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian Amazon basin

Amazon Basin

The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

, where it occurs mostly in the area south of the Amazon River

Amazon River

The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, in the states of Acre

Acre

The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...

, Amazonas and Rondônia

Rondônia

Rondônia is a state in Brazil, located in the north-western part of the country. To the west is a short border with the state of Acre, to the north is the state of Amazonas, in the east is Mato Grosso, and in the south is Bolivia. Its capital is Porto Velho. The state was named after Candido Rondon...

. The disease has also been diagnosed in Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

. The similar form in Colombia has been named Santa Marta fever.

Its main manifestation is a 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...

 hepatitis

Hepatitis

Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...

 which may kill in less than a week, and which characteristically affects children and young adults, and more males than females. It is accompanied also by an encephalitis

Encephalitis

Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...

 in many cases. The disease is highly lethal: in a study carried out in 1986 at Boca do Acre

Boca do Acre

Boca do Acre is a municipality located in the Brazilian state of Amazonas. Its population was 28,261 and its area is 22,349 km²....

, also in the Amazon, 39 patients out of 44 died in the acute phase of the disease. Survivors may develop chronic

Chronic (medicine)

A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...

 disease.

Symptoms and signs

Lábrea fever has a sudden onset, with jaundice

Jaundice

Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...

 (yellowing of the skin), anorexia

Anorexia (symptom)

Anorexia is the decreased sensation of appetite...

 (lack of appetite), hematemesis

Hematemesis

Hematemesis or haematemesis is the vomiting of blood. The source is generally the upper gastrointestinal tract. Patients can easily confuse it with hemoptysis , although the latter is more common.-Signs:...

 (vomiting

Vomiting

Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

 of blood), headache

Headache

A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

, fever

Fever

Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

 and severe prostration

Prostration

Prostration is the placement of the body in a reverentially or submissively prone position. Major world religions employ prostration either as a means of embodying reverence for a noble person, persons or doctrine, or as an act of submissiveness to a supreme being or beings...

. Death occurs by acute liver failure (ALF). In the last phase, neurological symptoms

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,...

 such as agitation, delirium

Delirium

Delirium or acute confusional state is a common and severe neuropsychiatric syndrome with core features of acute onset and fluctuating course, attentional deficits and generalized severe disorganization of behavior...

, convulsion

Convulsion

A convulsion is a medical condition where body muscles contract and relax rapidly and repeatedly, resulting in an uncontrolled shaking of the body. Because a convulsion is often a symptom of an epileptic seizure, the term convulsion is sometimes used as a synonym for seizure...

s and hemorrhagic coma

Coma

In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...

 commonly appear.

Etiology

Lábrea fever is a coinfection

Coinfection

In parasitology, coinfection is the term used to describe the simultaneous infection of a host by multiple pathogen species. In virology, coinfection can also refer to the simultaneous infection of a single cell by two or more virus particles...

 or superinfection

Superinfection

In virology, superinfection is the process by which a cell, that has previously been infected by one virus, gets coinfected with a different strain of the virus, or another virus at a later point in time. Viral superinfections of serious conditions can lead to resistant strains of the virus, which...

 of hepatitis D

Hepatitis D

Hepatitis D, also referred to as hepatitis D virus and classified as Hepatitis delta virus, is a disease caused by a small circular enveloped RNA virus. It is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a subviral satellite because it can propagate only in the...

 or delta virus and hepatitis B (HBV). The infection by delta virus may occur in a patient who already has the HBV, or both viruses may infect at the same time a previously uninfected patient. Delta virus can only multiply in the presence of HBV, therefore vaccination

Vaccination

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 HBV prevents infection. Thus, American and Brazilian scientists have determined that the delta virusa, virus, which is a small circular RNA virus

RNA virus

An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...

, is normally unable to cause illness by itself, due to a defect. When it is combined with HBV, Lábrea hepatitis may ensue. The main discovery of delta virus and HBV association was done by Dr. Gilberta Bensabath, a leading tropical virologist of the Instituto Evandro Chagas, of Belém

Belém

Belém is a Brazilian city, the capital and largest city of state of Pará, in the country's north region. It is the entrance gate to the Amazon with a busy port, airport and bus/coach station...

, state of Pará

Pará

Pará is a state in the north of Brazil. It borders the Brazilian states of Amapá, Maranhão, Tocantins, Mato Grosso, Amazonas and Roraima. To the northwest it also borders Guyana and Suriname, and to the northeast it borders the Atlantic Ocean. The capital is Belém.Pará is the most populous state...

, and her collaborators.

Infected patients show extensive destruction of liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 tissue, with steatosis

Steatosis

In cellular pathology, steatosis is the process describing the abnormal retention of lipids within a cell. It reflects an impairment of the normal processes of synthesis and elimination of triglyceride fat. Excess lipid accumulates in vesicles that displace the cytoplasm...

 of a particular type (microsteatosis, characterized by small fat droplets inside the cells), and infiltration of large numbers of inflammatory cells called morula cells, comprised mainly by macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s containing delta virus antigen

Antigen

An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...

s.

In the 1987 Boca do Acre study, scientists did an epidemiological survey and reported delta virus infection in 24% of asymptomatic HBV carriers, 29% of acute nonfulminant hepatitis B cases, 74% of fulminant hepatitis B cases, and 100% of chronic hepatitis B cases. The delta virus seems to be endemic

Endemic (epidemiology)

In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...

 in the Amazon region.

Treatment and prevention

Treatment is similar to hepatitis B, but due to its high lethality, more aggressive therapeutic approaches are recommended in the acute phase. In absence of a specific vaccine

Vaccine

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...

 against delta virus, the vaccine against HBV must be given soon after birth in risk groups.