Lassa fever is an acute viral illness caused by the Lassa virus, which is hosted by rodents, specifically the Mastomy natalensis species. Lassa fever is endemic in West Africa and has been mainly reported from Sierra Leone, Guinea, Liberia, and Nigeria.
Previous studies reported that 300,000 to 500,000 cases of Lassa fever and 5,000 deaths occur yearly across West Africa. Lassa virus is spread to humans primarily through direct or indirect contact with the urine, feces, or saliva of infected rats.
Human to human transmission can also occur through contact with infected secreta, blood, or contaminated medical equipment. The overall mortality rate of Lassa fever is approximately 1%, however, it increases to 15-20% for hospitalized patients. Early administration of Ribavirin and supportive care are the mainstay of treatment.
In January 2016, Nigeria reported that Lassa fever outbreak has occurred since August 2015 and they had more than 150 suspected cases of Lassa fever, including 82 deaths. Recently, there were imported cases in United States and Germany from Togo, a neighboring country to Nigeria. Notably, a local transmission case from the imported patient was also reported in Germany. Clinicians and public health officials need to remain alert to Lassa fever and to establish preparedness to identify and contain transmission.
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