Lassa fever

Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arenavirus family of viruses.  

Humans usually become infected with Lassa virus through exposure to food or household items contaminated with urine or faeces of infected Mastomys rats. The disease is endemic in the rodent population in parts of West Africa.  

Lassa fever is known to be endemic in Benin, Ghana, Guinea, Liberia, Mali, Sierra Leone, Togo and Nigeria, but probably exists in other West African countries as well.  

There is currently no licensed vaccine for Lassa fever, but several potential vaccines are in development. Despite not being licensed as a treatment for Lassa fever the antiviral drug ribavirin has been used in several countries as a therapeutic agent. However, there is still a need for a safe treatment with proven efficacy, and a range of potential treatments including immune therapies and drug therapies are currently being evaluated. No evidence supports the role of ribavirin as a treatment for Lassa fever. 

The incubation period of Lassa fever ranges from 2–21 days. The onset, when it is symptomatic, is usually gradual, starting with fever, general weakness and malaise. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. In severe cases facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop.