What is the history of Lassa fever?
Lassa fever was first described in the 1950s, and the viral particle was identified in 1969 from three missionary nurses who died in Lassa, Nigeria, after caring for an infected obstetrical patient. Lassa fever is one of the hemorrhagic fever viruses, occurring in West Africa sub-regions in similar areas as Ebola virus. Sierra Leone, Liberia, Ghana, and Nigeria are most often affected. Surrounding regions are also at risk, because the rodents that transmit the virus are very common throughout West through East Africa. There are 100,000 to 300,000 cases of Lassa fever each year in the world. Lassa fever heavily impacts Sierra Leone and Liberia in particular, where it causes an estimated 5,000 deaths and about 10%-16% of admissions to hospitals each year. Deaths are especially common in children. Case fatality is 1% in general (compared to 70% in Ebola virus). Severe cases have a case fatality of 15%.
An unusually intense outbreak developed in early 2018 in Nigeria with over 300 confirmed positive cases reported in the month of March. Cases were reported in Bauchi, Plateau, Edo, Ondo, and Ebonyi States. Sixteen health workers, at least four of whom died, were diagnosed as of Mar. 4, 2018. Along with high numbers, case fatality rates for this outbreak exceeded 20%. A Weekly Epidemiological Report has been maintained by the Nigeria Centre for Disease Control.
Nigerian Minister of Health, Professor Isaac Adewale, announced that vaccine against Lassa virus would be arriving by the end of 2018. Dr. Chikwe Ihekweazu, CEO of the Nigeria Centre for Disease Control, has stressed the important advances of improved awareness and expanded ability to test for Lassa fever virus in recent years. Dr. Ihekweazu has encouraged improved adherence to infection prevention measures and community sanitation efforts to control current and future outbreaks of Lassa fever. Lassa fever has rarely been diagnosed in the U.S. There have been only six diagnosed cases since 1969. The last case was diagnosed in May 2015, in New Jersey in a patient traveling from Liberia. U.S. cases have involved international travelers or immigrants who arrived with the infection after exposure to rodents in West Africa.
Among the scientists who have studied hemorrhagic fever viruses, Dr. Susan P. Fisher-Hoch, Professor of Epidemiology at the University of Texas School of Public Health, worked extensively with Lassa virus, conducting primate studies and investigating several outbreaks in Nigeria while working with the U.S. Centers for Disease Control and Prevention (CDC). While Deputy Branch Chief of the CDC Special Pathogens Laboratory, Division of Viral Diseases, she supervised the Sierra Leone Lassa Fever Research Unit and published major research articles on Lassa fever vaccines and other hemorrhagic fevers. Many students of epidemiology (the study of how diseases spread) are familiar with the story of her work with her husband, Dr. Joe McCormick, whom she married while he was Chief, Special Pathogens Laboratory, Level 4: Virus Hunters of the CDC. Dr. Fisher-Hoch was elected to the Women in Technology International Hall of Fame in 2008 for her extraordinary contributions to science and medicine.