Lassa Fever in the United States

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 Lassa fever is infrequently encountered in areas where the disease . . .