Arenaviruses

The Arenaviridae are a small group of viruses, containing several of considerable importance as human disease agents. They are listed in the Catalogue of Arthropod-Borne Viruses , not because they are arboviruses but because they have been discovered in large part by arbovirologists, working on details of arthropod-transmitted viruses. Most of the 14 members of the group have rodents as reservoir hosts, but they occasionally infect humans who imbibe or ingest the virus when accidentally consuming rodent-contaminated food and drink, or are otherwise in contact with an environment contaminated by rodent excreta. At least one of the viruses, however, Lassa virus, can pass directly from person to person. This happens particularly in hospital settings. Other Arenaviruses important in human disease are Junin (Argentine hemorrhagic fever), Machupo (Bolivian hemorrhagic fever) from South America, and the virus causing lymphocytic choriomeningitis (LCM). Six of the viruses - Junin, Machupo, Pichinde, Tacaribe, Lassa, and LCMs have infected laboratory workers. (Because Lassa fever is covered elsewhere in this work, it will not be treated here in any detail.) Virus Morphology, Size, and Structure Electron micrographic studies of infected cells reveal round, oval, or pleomorphic budding particles with mean diameters of 110 to 130 nanometers. The envelopes, which have spikes, are derived from the plasma membranes of the host cell by budding. The interior contains variable numbers of electron-dense granules measuring 20 to 25 nanometers and resembling ribosomes. These sandy grains gave rise to the name Arenavirus because arena means “sand” (Rowe et al. 1970). The exact composition of this core material and its derivation are as yet uncertain. The virions are enveloped RNA-containing nucleocapsids. The genome consists of two single-stranded RNA molecules (Lehmann-Grube 1988).