The Fight Against Lassa Fever

1200px-Lassa_virus.JPGUnlike Ebola, most people may have not heard of Lassa Fever Virus, a similarly deadly hemorrhagic fever, which most recently saw an outbreak in West Africa in 2018. First observed when two nuns contracted the disease in 1969, Lassa has since been recognized as a global threat by the WHO. Those who survive the disease are left with unspoken negative economic and social impacts. As outbreaks continue, the search for a vaccine and containment methods are showing promising results.


Lassa virus is present in many West African countries such as Nigeria, Sierra Leone, Liberia, Guinea, and others. Multimammate rats (Mastomys natalensis) serve as the reservoir for the virus. In West Africa, these rats are sometimes eaten and handled, and often invade food stores. The virus is spread via the rats’ urine. Even when dry, the virus can be transmitted through airborne particles that are aerosolized upon sweeping. Once the virus has made the jump from the rats to humans, it can be transmitted from human to human through bodily fluids (CDC).

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Every year, there are approximately between 100,000 and 500,000 cases of Lassa fever, and 5000 deaths. The incubation period for Lassa virus is between two and twenty-one days and symptoms begin very gradually. For an estimated 80% of patients, the symptoms of Lassa fever are very mild and undiagnosed. However, the remaining percentage of patients can experience hemorrhaging, respiratory distress, vomiting, facial swelling, pain, shock, and sometimes even death within two weeks by multisystem organ failure. Poor prognosis is generally associated with “edema of the face and neck, abdominal and retrosternal pain, enlarged lymph nodes, and/or hemorrhage in the conjunctiva or mucosal surfaces” (Warner, Safronetz, & Stein, 2018). Because of the rural nature of the regions in which Lassa fever occurs, it can be difficult to accurately measure infection and mortality rates. While most estimates of death rate are between 5-20%, recent studies have shown upwards of 60% mortality “in acutely ill patients from endemic regions” (Hartnett et al., 2015). Most organizations agree, at least, that mortality is increasing (Hartnett et al., 2015; Sogoba, Feldmann, & Safronetz, 2012; Warner et al., 2018).

The impact that this deadly virus has on human life is astounding. Between 25-30% of those infected with Lassa virus will become partially to fully deaf sometime after infection. Half of those who experience deafness will recover their hearing partially or entirely. However, those who do not are forced to adapt to a completely different lifestyle (Mateer, Huang, Shehu, & Paessler, 2018).  Among the hardest hit are pregnant women, especially in their third term, who have the highest death rate from the virus. For patients who survive, economic problems come from their time in the sick ward and even after due to social stigma, which uninfected relatives face as well.

Luckily for future generations, recent research has been very promising.  Real-time genomic sequencing of the virus is helping to decrease response times to outbreaks and set priorities for control (Siddle et al., 2018).  For prevention, four vaccine candidates are currently ready for phase III (human) testing for efficacy (Warner et al., 2018).  While there is still progress to be made, the fight against Lassa Fever Virus is by no means at a standstill, and hope for further control of the virus remains high.

Edited by Jin Yoo.


Hartnett, J. N., Boisen, M. L., Oottamasathien, D., Jones, A. B., Millett, M. M., Nelson, D. S., . . . Branco, L. M. (2015). Current and emerging strategies for the diagnosis, prevention and treatment of Lassa fever. Future Virology, 10(5), 559-584. doi:10.2217/fvl.15.41

Lassa Fever | CDC. (n.d.). Retrieved from

Mateer, E. J., Huang, C., Shehu, N. Y., & Paessler, S. (2018). Lassa fever–induced sensorineural hearing loss: A neglected public health and social burden. PLOS Neglected Tropical Diseases, 12(2), e0006187. doi:10.1371/journal.pntd.0006187

Siddle, K. J., Eromon, P., Barnes, K. G., Mehta, S., Oguzie, J. U., Odia, I., . . . Happi, C. T. (2018). Genomic Analysis of Lassa Virus during an Increase in Cases in Nigeria in 2018. New England Journal of Medicine, 379(18), 1745-1753. doi:10.1056/NEJMoa1804498

Sogoba, N., Feldmann, H., & Safronetz, D. (2012). Lassa Fever in West Africa: Evidence for an Expanded Region of Endemicity. Zoonoses and Public Health, 59(s2), 43-47. doi:10.1111/j.1863-2378.2012.01469.x

Warner, B. M., Safronetz, D., & Stein, D. R. (2018). Current research for a vaccine against Lassa hemorrhagic fever virus. Drug design, development and therapy, 12, 2519-2527. doi:10.2147/DDDT.S147276

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