 In 1979 , Conteh began working with the CDC and team leader Joseph B. McCormick at the Nixon Methodist Hospital in Segbwema . Conteh became Medical Superintendent of the hospital in 1980 . The Sierra Leone Civil War broke out in 1991 , forcing the CDC to close their program and move to Guinea . The hospital was destroyed in the conflict and the spread of Lassa fever grew worse . During the civil war , the Natal multimammate mouse infested abandoned houses , increasing the likelihood of infection . 
