Lassa fever is an acute viral hemorrhagic disease that occurs in West Africa. It is caused by a virus, called the Lassa virus.
It was named after a town in Borno state – Northern Nigeria – which was where the first cases of the illness first occurred. Lassa fever was first described in the 1950s. However, the Lassa virus was first identified in 1969 when two missionary nurses died from the disease in Nigeria. They were infected after providing health care for a pregnant woman who was infected.
Lassa fever is an infectious disease but is not as infectious as Ebola; neither is it as deadly as Ebola. And it is a zoonotic disease. The animal that serves as a host or reservoir for the Lassa virus is a rodent that is commonly called “multimammate” rat. Multimammate rats belong to the genus Mastomys. These rats do not become ill when they are infected with the virus; but they shed the virus in their faeces and urine.
Not everyone who is infected with the Lassa virus develops symptoms of the disease; as a matter of fact, about 80% of those infected do not have symptoms. One out of five infections become severe disease that affects many organs (such as kidneys, liver, and spleen).
This viral hemorrhagic fever is known to be endemic in certain countries, including Nigeria, Ghana, Mali, Benin, Sierra-Leone, and Liberia. Countries in West Africa where it has not been found to be endemic are at risk because the “multimammate” rat is common in the West African region. In October 2011, it was diagnosed for the first time in Ghana. And in November 2014, it was first diagnosed in Benin. In February 2009, Mali reported its first case which occurred in a traveller. In Burkina Faso and Cote d’Ivoire, isolated cases have been reported; and in Togo, serologic evidence of the infection has been documented.
This disease occurs in both males and females. And it affects all age groups.
In West Africa, there are about 100,000 to 300, 000 Lassa virus infections every year. And about 5000 people die as a result of Lassa fever in West Africa, every year. These figures are just estimates that are not accurate because proper monitoring systems for this disease are not functional. Every year, in some parts of Liberia and Sierra Leone, 10% – 16% of people who are admitted into the hospitals have Lassa fever. This gives you a bit of a picture how much this disease affects some countries.
It is endemic in Nigeria, Ghana, Mali, Liberia, Sierra Leone, Guinea and Benin. Countries that are close to these countries (neighbouring countries) where Lassa fever is commonly found are also at risk of having cases of this disease because the host (multimammate rats) are common in West Africa. Other countries where it has been found are Gambia, Togo, Burkina Faso, Cote d’Ivoire, Central African Republic, and Senegal.