Virus Morphology, Size, and Structure

Electron micrographic studies of infected cells re­veal round, oval, or pleomorphic budding particles with mean diameters of IlO 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 nucleo- capsids. The genome consists of two single-stranded RNA molecules (Lehmann-Grube 1988).