 Conteh spent his professional career working with patients suffering from Lassa fever , a viral haemorrhagic fever endemic to West Africa . Lassa fever was first brought to the attention of the public in 1969 during an outbreak in Nigeria . Identified in 1972 , the disease is known to spread through its host , the Natal multimammate mouse ( Mastomys natalensis ) , and infects an estimated 300 @,@ 000 people and results in 5000 deaths annually in Sierra Leone , Liberia , and Guinea . In 1976 , a nosocomial outbreak in the Panguma Catholic Hospital attracted attention in the United States . In response , the Centers for Disease Control and Prevention ( CDC ) established research programs in Segbwema , Kenema , and Panguma to study the disease . 
