Lassa Fever

Lassa fever is a viral infection caused by the Lassa virus. The virus is largely confined to West Africa. Epidemics have been recognized in Nigeria, Sierra Leone and Zaire. It is highly contagious and can cause a severe or fatal illness.

A rat serves as a reservoir for the illness. Humans are primarily infected by being bitten by an infected rodent or eating food contaminated with rat excretions. Infection is also possible through the inhalation of dried infected urine. Person to person transmission is possible through contamination of skin breaks with infected blood. As the virus is present in bodily secretions such as urine, saliva, and semen, it can be spread through sexual contact as well. Hospitals and dispensaries are ideal environments for the spread of Lassa, and the worst epidemics documented have occurred in these places.

The incubation period of lassa fever is 7 to 21 days. The illness is characterized by high fever, sore throat, muscle aches, weakness, skin rash (with hemorrhages), headache, abdominal pain, vomiting, and diarrhea.

The number of cases of Lassa fever annually is estimated at 200,000 - 400,000 cases with several thousand fatal. Overall mortality among hospital cases is about 15%. In untreated cases, mortality rises to 60%. In endemic areas, antibodies to the virus in the population may reach 40%.

If a person has traveled to West Africa and has a severe fever within 21 days of return, the illness should be reported to a physician who should test for lassa fever. Due to the highly contagious nature of this illness and because the mode of transmission is not totally clear, strict isolation precautions are to be followed. Patients may excrete the virus weeks after recovery.

At this time, the treatment of lassa fever is symptomatic (treating the symptoms of high fever, etc.), supportive (making the infected person comfortable) and preventive (following strict isolation procedures). Lassa Fever has been successfully treated with ribavirin as well.

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Diseases