Lassa Fever in the United States

Abstract

LASSA fever, first identified in northeastern Nigeria in 1969,¹ is endemic in much of western Africa. Mastomys natalensis, a rat that is common around human habitations in the region, is the host of enzootic Lassa fever virus.² The virus is spread to humans primarily through the urine of infected rats and is also transmissible from person to person. Its incubation period ranges from 7 to 18 days.³ Lassa fever virus may cause as many as 300,000 human infections and 5000 deaths per year in areas where the disease is endemic.⁴