Arenaviruses are a group of about twelve viruses, mostly restricted to Africa and South America, each infecting a special species of rodent. In the rodent, the harmless infection stays for life. In humans, however, these viruses cause such severe diseases as Lassa fever, South American haemorrhagic fevers, and LCM (lymphocytic choriomeningitis).
Arenaviruses were named after the Latin word for sand because of their granular interior. They are large RNA viruses that contain dense, ribosome-sized particles that give the appearance of sand particles when viewed by an electron microscope.
The natural hosts of these viruses are generally rats, bats, and mice. The viruses are then shed in the feces and urine to contaminate food and water. When humans consume the infected foods, they contract the infection. Some of them cause meningitis and various hemmorrhagic fevers. Other infections include the following: Lassa Fever, lymphocytic choriomeningitis, and Argentinean and Bolivian hemorrhagic fevers.
The same viruses were also identified as the cause of an encephalitis outbreak in St. Louis MO in 1933. In other areas, they have such names as the following: Amapari, Junin, Lassa, Latino, Machupo, Parana, Pichinde, Tacaribe, Tamiami. The Junin virus caused the Argentinian hemmorrhagic fever in 1953, producing a 20% mortality rate. The Bolivian brand (Machupo), also called the black Typhus, reached a 30% mortality rate. In 1969, Lassa fever came to the attention of western scientists when American nurses were stricken in a Nigerian village. There, the mortality rate reached 60% in one hospital alone.
The Lassa virus has as its main residence a particular rodent (Mastomys natalensis), that thrives in sub-Saharan Africa. Breathing in dust contaminated with dried urine from an infected rodent passes the disease along in much the same way as with the Hantavirus. Twenty to forty thousand people suffer from the disease each year, with several thousand dying.