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Definition

Lassa fever is a type of viral hemorrhagic fever caused by the Lassa virus.[1] Many, but not all, of those infected by the virus do not develop symptoms.[1] The disease is usually first spread to people via contact with the urine or feces of an infected multimammate mouse;[1] there is currently no vaccine available.[2]

Lassa Virus (51719108882).jpg

Signs and symptoms

Onset of symptoms is typically 7 to 21 days after exposure.[3][3][4] These symptoms may include fever, tiredness, weakness, and headache.[3] In 20 percent of people more severe symptoms such as bleeding gums, breathing problems, vomiting, chest pain, or very low blood pressure may occur.[3]

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Virology

Lassa viruses are enveloped, single-stranded, bisegmented, ambisense RNA viruses.[5][6] Their genome is contained in two RNA segments that code for two proteins each, one in each sense, for a total of four viral proteins.[7][8]

Lassa virus.JPG

Transmission

Lassa virus commonly spreads to humans from other animals, specifically the natal multimammate mouse or African rat, also called the natal multimammate rat, Mastomys natalensis.[9] One of the most common mouse in equatorial Africa, common in human households and eaten as a delicacy in some areas.[9][10]

Mastomys natalensis.jpg

Pathogenesis

In terms of the mechanism of Lassa fever, currently the chain of events that occur during disease development is not known.[11] However, according to one review in 2012, a possible pathogenesis could be infection-triggered induction of uncontrolled cytokine expression. According to the same review the hypothesis would be supported by a case in which - proinflammatory cytokines, interferon (gamma) and tumor necrosis factor (alpha) all rose to very high levels before death of an infected individual with the virus.[11]

Cytokine release.jpg

Diagnosis

The evaluation of this infection is done by enzyme-linked immunosorbent serologic assays, which detect certain antibodies; RT-PCR can be used as well to detect the disease.[12] In cases with abdominal pain, in countries where Lassa is common, Lassa fever is often misdiagnosed as appendicitis and intussusception which delays treatment.[13]

ELISA reader with microtiter plate.jpg

Treatment

Treatment is directed at addressing dehydration and improving symptoms,[1] all persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of. The antiviral medication ribavirin has been recommended,[1] but evidence to support its use is weak.[14]

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Prognosis

About 15 to 20 percent of hospitalized people with Lassa fever will die from the illness. The overall case fatality rate is estimated to be 1 percent, but during epidemics, mortality can climb as high as 50 percent.[15]

Hospital bed at Pok Oi Hospital.jpg

Epidemiology 1

Lassa high risk areas are near the western and eastern extremes of West Africa. As of 2018, the Lassa belt includes Guinea, Nigeria, Sierra Leone and Liberia.[16] As of 2003, 10 to 16 percent of people in Sierra Leone and Liberia admitted to the hospital had the virus.[9] The case fatality rate for those who are hospitalized for the disease is about 13 percent. [17]

Lassa fever Outbreak Distribution Map.svg

Epidemiology 2

An outbreak of Lassa fever occurred in Nigeria during 2018 and spread to 18 of the country's states; it was the largest outbreak of Lassa fever recorded.[18][19][20] On 25 February 2018, there were 1081 suspected cases and 90 reported deaths; 317 of the cases and 72 deaths were confirmed as Lassa which increased to a total of 431 reported cases later in 2018.[21]

Nigeria Base Map.png

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 "Lassa fever". www.who.int. Retrieved 20 April 2022.
  2. ↑ Yun, N. E.; Walker, D. H. (2012). "Pathogenesis of Lassa Fever". Viruses. 4 (12): 2031–2048. doi:10.3390/v4102031. PMC 3497040. PMID 23202452.
  3. ↑ 3.0 3.1 3.2 3.3 "Signs and Symptoms | Lassa Fever | CDC". www.cdc.gov. 6 March 2019. Archived from the original on 9 July 2017. Retrieved 18 June 2019.
  4. ↑ Greenky D, Knust B, Dziuban EJ (May 2018). "What Pediatricians Should Know About Lassa Virus". JAMA Pediatrics. 172 (5): 407–408. doi:10.1001/jamapediatrics.2017.5223. PMC 5970952. PMID 29507948.
  5. ↑ Jamie Dyal and Ben Fohner Lassa virus Archived 25 March 2013 at the Wayback Machine Stanford University Humans and Viruses Class of 2005, n.d. accessed 9 May 2018
  6. ↑ Lashley, Felissa R., and Jerry D. Durham. Emerging Infectious Diseases: Trends and Issues. New York: Springer Pub., 2002. Print.
  7. ↑ Ridley, Matt. Genome: The Autobiography of a Species in 23 Chapters. New York: HarperCollins, 1999. Print.
  8. ↑ "Lassa virus RefSeq Genome". Archived from the original on 17 July 2018. Retrieved 20 April 2022.
  9. ↑ 9.0 9.1 9.2 Richmond, J. K.; Baglole, D. J. (2003). "Lassa fever: Epidemiology, clinical features, and social consequences". BMJ. 327 (7426): 1271–1275. doi:10.1136/bmj.327.7426.1271. PMC 286250. PMID 14644972.
  10. ↑ Werner, Dietrich (2004). Biological Resources and Migration. Springer. pp. 363. ISBN 978-3-540-21470-0.
  11. ↑ 11.0 11.1 Yun, Nadezhda E.; Walker, David H. (9 October 2012). "Pathogenesis of Lassa Fever". Viruses. 4 (10): 2031–2048. doi:10.3390/v4102031. ISSN 1999-4915. Archived from the original on 15 March 2022. Retrieved 22 April 2022.
  12. ↑ "Diagnosis | Lassa Fever | CDC". www.cdc.gov. 4 March 2019. Retrieved 25 April 2022.
  13. ↑ Dongo, A. E.; Kesieme, E. B.; Iyamu, C. E.; Okokhere, P. O.; Akhuemokhan, O. C.; Akpede, G. O. (2013). "Lassa fever presenting as acute abdomen: a case series". Virology Journal. 10: 124. doi:10.1186/1743-422X-10-123. PMC 3639802. PMID 23597024.
  14. ↑ Eberhardt, Kirsten Alexandra; Mischlinger, Johannes; Jordan, Sabine; Groger, Mirjam; Günther, Stephan; Ramharter, Michael (1 October 2019). "Ribavirin for the treatment of Lassa fever: A systematic review and meta-analysis". International Journal of Infectious Diseases. 87: 15–20. doi:10.1016/j.ijid.2019.07.015. ISSN 1201-9712. Retrieved 26 April 2022.
  15. ↑ Centers for Disease Control and Prevention, "Lassa Fever, Signs and Symptoms" Archived 9 July 2017 at the Wayback Machine
  16. ↑ David Greenky, Barbara Knust, Eric J. DziubanWhat Pediatricians Should Know About Lassa Virus. JAMA Pediatr. 2018;172(5):407-408. doi:10.1001/jamapediatrics.2017.5223
  17. ↑ "Acute and Delayed Deaths after West Nile Virus Infection, Texas, USA, 2002–2012". CDC. CDC. Archived from the original on 3 February 2022. Retrieved 23 April 2022.
  18. ↑ Maxmen, Amy (15 March 2018). "Deadly Lassa-fever outbreak tests Nigeria's revamped health agency". Nature. 555 (7697): 421–422. Bibcode:2018Natur.555..421M. doi:10.1038/d41586-018-03171-y. PMID 29565399.
  19. ↑ "On the frontlines of the fight against Lassa fever in Nigeria". World Health Organization. March 2018. Archived from the original on 20 March 2018. Retrieved 20 March 2018.
  20. ↑ Beaubien, Jason (19 March 2018). "Nigeria Faces Mystifying Spike in Deadly Lassa Fever". NPR. Archived from the original on 19 March 2018. Retrieved 20 March 2018.
  21. ↑ "Lassa Fever – Nigeria". World Health Organization. 1 March 2018. Archived from the original on 6 March 2018. Retrieved 12 March 2018.
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