Lassa fever was first reported in the town of Lassa, Borno State in Nigeria, in 1969. Subsequent outbreaks occurred in Sierra Leone and Liberia in 1972 and led the CDC to set up a research programme for Lassa fever in Sierra Leone in the mid-1970s, although this was closed down when researchers fled fighting during the civil war. The mission hospital in Sierra Leone where the Lassa fever programme was based was overtaken by the Rebels. Throughout the civil war in Sierra Leone (1991-2002) and especially after the 1997 political coup, many health facilities in the country were destroyed and much of the public health infrastructure was damaged. During the war, some of the international research capacity for Lassa fever moved to the neighbouring Guinea, where the disease is also endemic, although the Sierra Leonean doctor Aniru Conteh was instrumental in setting up and managing a specialist Lassa ward at Kenema Government Hospital, with support from the British medical relief organisation Merlin. Epidemics of Lassa fever were reported in Sierra Leone in the 1990s and early 2000s. The civil war and subsequent political instability resulted in widespread displacements of people and the use of sub-par housing materials and temporary accommodation, almost certainly contributing to a number of serious outbreaks.
Meanwhile in Nigeria, Lassa fever research and clinical care has centered around the development of Irrua Specialist Teaching hospital, which was declared a Centre of excellence for the Control and Management of Lassa fever in Nigeria in 2001. The Institute of Lassa fever Control at Irrua was inaugurated in 2007. The objective of the institute is to study and respond to Lassa epidemics in a more comprehensive way. Since the establishment of the institute, outbreaks of Lassa feverhave happened annually and lasted for longer periods, suggesting are signs that Lassa fever is becoming a year round disease. The Nigeria Centre for Disease Control (NCDC) was established in 2011 in response to public health emergencies and to improve epidemic preparedness, and is the lead agency in the fight against Lassa fever in Nigeria. In 2018, there was an epidemic of Lassa fever in Nigeria where cases were reported across 20 states including the Federal Capital Territory, with most within Edo and Ondo states. This was the largest outbreak of Lassa ever recorded.