History
The first arenavirus to be discovered was the one causing LCM in mice and monkeys; it was reported in 1934 by C. Armstrong and R. D. Lillie. Later studies showed that the virus was present in feral Mus musculus (the common house mouse) and accounted for a scattering of human cases annually in Europe and America.
More commonly, those cases were seen in personnel who were handling laboratory animals, particularly white mice and hamsters. The agent itself was characterized morphologically by electron microscopy, and later investigated in serologic, biochemical, and biophysical studies. No serologic relatives were found, and over several decades, only scattered cases and outbreaks have been reported in America and Europe.In 1957, a virus named Tacaribe was recovered from a fruit-eating bat in Trinidad, West Indies (Downs et al. 1963). This agent remained unclassified. Meanwhile a disease was observed among field workers in the northern provinces of Argentina that occurred at harvest time and caused considerable mortality. A virus subsequently named Junin (Parodi et al. 1958) was recovered from these patients, and the disease was named Argentinian hemorrhagic fever (AHF). Cases occur annually, and there have been epidemics of the disease over the past 30 years.
A particularly virulent infection broke out in the small town of San Joaquin, Beni Department, in the Amazonian lowlands of Bolivia. In due course it was called Bolivian hemorrhagic fever (Johnson et al. 1965). The outbreak was checked, however, once the rodent host of the Machupo virus that caused the disease was implicated and rodent control mechanisms were instituted. Since then Machupo virus has “gone underground”; no further outbreaks have been reported and little further epidemiological work is being done on the disease.
In January 1969, another of the arenaviruses was forcefully brought to the attention of Western medicine, with an outbreak among medical personnel in Lassa, northeastern Nigeria (Buckley, Casals, and Downs 1970). At least seven more outbreaks of the disease subsequently named Lassa fever have taken place since then, involving about 450 patients and almost 125 deaths. The virus appears to have a natural cycle of transmission in rodents but, as previously mentioned, can spread from human to human.