Posted by ajcann on October 19, 2008
On 12 September 2008, a tourist guide organising safari trips in Lusaka, Zambia, was evacuated in a critical condition to Johannesburg, South Africa. She was admitted to a clinic where she died on 14 September about 10 days after the onset of symptoms. The symptoms included a prodromal phase with fever, myalgia, vomiting, diarrhoea, followed by rash, liver dysfunction and convulsions. Cerebral oedema was detected on scan examination. No laboratory specimen was available for investigation. A total of four cases have now been reported.
On 12 October 2008, the National Institute for Communicable Diseases in South Africa provided preliminary evidence that the causative agent of the disease was a virus from the Arenaviridae family. Specimens were shipped to the United States Centers for Disease Control and Prevention in Atlanta for additional investigations.
Arenaviruses are enveloped viruses (about 120 nm diameter) with a bi-segmented negative strand RNA genome. The typical image in electronic microscopy showing grainy ribosomal particles (from arena, the Latin for "sand") inside the virions gave the name to this family of viruses. The prototype is the Lymphocytic Choriomeningitis (LCM) virus (LCMV), isolated in 1933 in North America from a human case with aseptic meningitis. Cases caused by LCMV occur worldwide. Other arenaviruses causing hemorrhagic fevers were reported in South America, causing sporadic cases or limited outbreaks: Junín virus in 1958 in Argentina, Machupo virus in 1963 in Bolivia, Guanarito virus in 1990-1991 in Venezuela, Sabia virus in 1990 in Brazil and more recently Chapare virus in 2004 in Bolivia. In West Africa, Lassa virus was identified in Nigeria in 1969. It causes thousands of cases each year in Sierra Leone, Liberia, Guinea and Nigeria. However, only limited data are available to assess the real incidence of Lassa fever in Africa.
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