Ebola and Marburg are closely related, newly emergent viruses that have in recent years caused epidemics in central Africa, with very high rates of mortality. Hantavirus occurs in many different parts of the world and is spread to humans from field rodents via microscopic bits of their excretions that get into the air and are inhaled. It was originally known as a disease of Asia and Europe that primarily attacked the kidneys, but a more deadly pulmonary form of hantavirus infection has more recently caused numerous fatalities in the United States, Chile, and other countries. Lassa fever, also spread to humans from rodent excretions, occurs primarily in W Africa. Closely related to the Lassa virus are the Junin and Machupo viruses, which have caused outbreaks of hemorrhagic fever in South America. Yellow fever, transmitted by the bite of a mosquito, still occurs in tropical areas despite largely successful control efforts. Dengue hemorrhagic fever, also spread by mosquitoes, has in recent years caused many fatalities among children in tropical countries.
There is usually no specific treatment to combat the viruses that cause hemorrhagic fevers. One exception is the drug ribavirin, which has been effective in treating Lassa fever and has also been used to treat a form of hantavirus infection and Crimean-Congo hemorrhagic fever. Treatment generally consists of such supportive measures as the replacement of lost blood, the maintainence of fluid balance, and the alleviation of symptoms. Survival depends largely upon the virulence of the virus strain and the quality of treatment.
See R. Reston, The Hot Zone (1994).
The vector is the vesper mouse (Calomys callosus), a rodent indigenous to northern Bolivia. Infected animals are asymptomatic and shed virus in excretions, by which humans are infected. Evidence of person-to-person transmission of Machupo virus exists but is believed to be rare (Kilgore, et. al, 1995).
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. A vaccine being developed for the genetically related Junín virus which causes Argentine hemorrhagic fever has shown evidence of cross-reactivity with Machupo virus and may be an effective prophylactic measure for people at high risk of infection.
There are no cures or immunisations for this disease, although those who have contracted it are immune. Treatment options are limited, mostly to supportive care, but are sometimes successful if started early.