Lassa Fever

Lassa fever is an acute viral disease spread by an African rat. The disease is named after a town in Nigeria and was first documented in 1969.  It is endemic to West Africa.

Cases have been reported in Sierra Leone, Liberia, Guinea, Nigeria, Benin, Ghana, Mali and Togo with an estimated 100,000 - 300,000 cases annually and 5,000 deaths. Many cases have no symptoms.

The reservoir of the disease is a rodent, Mastomys natalensis. The virus is transmitted to humans by inhalation and ingestion. The rodents shed the virus in urine and droppings and food may be contaminated. It can also be transmitted from human to human by secretions, blood and excretions.

Those most at risk are people living in endemic areas with exposure to the rat.

The risk to travellers is very low, however, individuals visiting friends and relatives in areas of risk would have a higher risk contracting Lassa Fever.

There is no vaccine currently available.

Lassa fever first attracted international attention when a “mystery febrile illness” was reported within a group of missionary nurses in 1969.  Two of the nurses died as well as a pathologist who performed an autopsy. The third nurse was evacuated to the United States where she was diagnosed with Lassa fever.

The virus was first isolated in the Yale School of Medicine and this discovery was linked back to the missionary outbreak.