BHF was first identified in 1959 by a research group led by Karl Johnson, an ambisense RNA virus of the Arenaviridae family. The mortality rate is estimated at 5 to 30 percent. Due to its pathogenicity, Machupo virus requires Biosafety Level Four conditions, the highest level.
In February and March
2007, some 20 suspected BHF cases (3 fatal) were reported to the El Servicio
Departamental de Salud (SEDES) in Beni Department, Bolivia, and in February 2008, at least 200
suspected new cases (12 fatal) were reported to SEDES. In November 2011, a
SEDES expert involved in a serosurvey to determine the extent of Machupo virus
infections in the Department after the discovery of a second confirmed case
near the departmental capital of Trinidad in November, 2011, expressed concern about expansion of the virus'
distribution outside the endemic zone in Mamoré and Iténez provinces.
The vector is the vesper mouse Calomys callosus, a rodent indigenous to northern Bolivia. Infected animals are asymptomatic and shed the virus in excreta, thereby infecting humans. Evidence of person-to-person transmission of BHF exists but is believed to be rare.
The infection has a slow onset with fever, malaise, headache and muscular pains. Petechiae (blood spots) on the upper body and bleeding from the nose and gums are observed when the disease progresses to the hemorrhagic phase, usually within seven days of onset.
Measures to reduce contact between the vesper mouse and humans have effectively limited the number of outbreaks, with no cases identified between 1973 and 1994. Although, there are no cures or immunization for the disease, a vaccine developed for the genetically related Junín virus which causes Argentine hemorrhagic fever has shown evidence of cross-reactivity to Machupo virus and may therefore be an effective prophylactic measure for people at high risk of infection. Post infection (and providing that the person survives the infection), those that have contracted BHF are usually immune to further infection of the disease.
Bolivian hemorrhagic fever was one of three hemorrhagic fevers and one of more than a dozen agents that the United States researched as potential biological weapons before the nation suspended its biological weapons program (Wikipedia, 2012).