Lábrea fever
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'''Lábrea fever''', also known as '''Lábrea's black fever''' and '''Lábrea hepatitis''', is a lethal [[tropical disease|tropical]] [[virus|viral infection]] discovered in the 1950s in the city of [[Lábrea]], in the [[Brazil|Brazilian]] [[Amazon basin]], where it occurs mostly in the area south of the [[Amazon River]], in the states of [[Acre]], [[Amazonas State, Brazil|Amazonas]] and [[Rondônia]]
. The disease has also been diagnosed in [[Colombia]] and [[Peru]]. The similar form in Colombia has been named '''Santa Marta fever'''.
Its main manifestation is a [[fulminant]] [[hepatitis]] 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]] in many cases. The disease is highly lethal: in a study carried out in 1986 at [[Boca do Acre]], also in the Amazon, 39 patients out of 44 died in the [[Acute (medical)|acute]] phase of the disease.<ref name=Bensabath_1987>{{cite journal | author=Bensabath G, Hadler SC, Soares MC, Fields H, Dias LB, Popper H, Maynard JE | title=Hepatitis delta virus infection and Labrea hepatitis. Prevalence and role in fulminant hepatitis in the Amazon Basin | journal=JAMA | year=1987 | pages=479–83 | volume=258 | issue=4 | pmid=3599343}}</ref> Survivors may develop [[chronic (medicine)|chronic]] disease.
==Symptoms and signs==
Lábrea fever has a sudden onset, with [[jaundice]] (bilious color of the skin), [[anorexia (symptom)|anorexia]] (lack of appetite), [[hematemesis]] (blood [[vomits]]), [[headache]], [[fever]] and severe [[prostration]]. Death occurs by [[acute liver failure]] (ALF). In the last phase, [[neurology|neurological symptoms]] such as agitation, [[delirium]], [[convulsion]]s and hemorrhagic [[coma]] commonly appear.
==Etiology==
Lábrea fever is a [[coinfection]] or [[superinfection]] of [[hepatitis D]] or delta virus and [[hepatitis B]] (HBV).<ref name=Bensabath_1987 /> 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]] against HBV prevents infection. Thus, American and Brazilian scientists have determined that the delta virusa, virus, which is a small circular [[RNA virus]], 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]], state of [[Pará]], and her collaborators.
Infected patients show extensive destruction of [[liver]] tissue, with [[steatosis]] 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]]s containing delta virus [[antigen]]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 (epidemiology)|endemic]] 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]] against delta virus, the vaccine against HBV must be given soon after birth in [[risk group]]s.
==References==
<references />
* {{cite book | author = Specter SC (Ed.).| title = Viral Hepatitis: Diagnosis, Therapy, and Prevention | edition = | publisher = Humana Press | year = 1999| id = ISBN 0896034240 }}
* {{cite journal | author=da Fonseca JC | title=[Hepatitis fulminant in Brazilian Amazon] | journal=Rev Soc Bras Med Trop | year=2004 | pages=93–5 | volume=37 Suppl 2 | pmid=15586904}}
*{{cite journal | author=Bensabath G, Soares Mdo C | title=[The evolution of knowledge about viral hepatitis in Amazon region: from epidemiology and etiology to the prophilaxy] | journal=Rev Soc Bras Med Trop | year=2004 | pages=14–26 | volume=37 Suppl 2 | pmid=15586892}}
* {{cite journal | author=Fonseca JC, Souza RA, Brasil LM, Araujo JR, Ferreira LC | title=Fulminant hepatic failure in children and adolescents in Northern Brazil | journal=Rev Soc Bras Med Trop | year=2004 | pages=67–9 | volume=37 | issue=1 | pmid=15042190 | doi=10.1590/S0037-86822004000100019}}
[[Category:Viral diseases|Labrea fever]]
[[Category:Tropical diseases|Labrea fever]]
[[Category:Hepatology|Labrea fever]]