Lassa virus

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This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see Lassa fever.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [2]


Lassa fever is caused by the Lassa virus, a member of the zoonotic Arenaviridae family. It is an enveloped, single-stranded, bisegmented RNA virus. The natural reservoir of Lassa virus is the Mastomys natalensis rodent (multimammate rat/mouse) that sheds the virus in urine and fecal droppings.

Microbiological Characteristics



  • Lassa virus belongs to Arenaviridae.[2]
  • The Arenaviridae are a family of viruses whose members are generally associated with rodent-transmitted diseases in humans (zoonotic). Each virus usually is associated with a particular rodent host species in which it is maintained.



  • Lassa virus genome is contained in two RNA segments, each of which encodes 2 viral proteins (total 4 viral proteins)[3][4]
  • Nucleotide studies of the genome have shown that Lassa has four lineages: Three in Nigeria and a fourth in Guinea, Liberia, and Sierra Leone. The Nigerian strains are thought to be ancestral to the others.[8].

Natural Reservoir

  • The most common natural reservoir of Lassa virus is the rodent, Mastomys natalensis. Mastomys natalensis is commonly known as the “multimammate rat/mouse” due to the female’s multiple and prominent mammary glands.
  • The mastomys rodents are abundant in the Savannas and forests of West, Central, and East Africa.
  • Once infected, the rodent is able to excrete the virus in the urine and feces for an extended time period. Mastomys rodents breed frequently, produce large numbers of offspring, and commonly inhabit human homes with food storage. All of these factors contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.
Mastomys natalensis or the natal multimammate mouse.[9]
Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.[9]


The images below display key features of the Lassa virus.


  1. "Taxonomy browser (Lassavirus)".
  2. "The Centers for Disease Control and Prevention".
  3. "Genome:The autobiography of a species in 23 chapters". Nat Genet. 24 (1): 21. 2000. doi:10.1038/71638. PMID 10615121.
  4. Moshkoff DA, Salvato MS, Lukashevich IS (2007). "Molecular characterization of a reassortant virus derived from Lassa and Mopeia viruses". Virus Genes. 34 (2): 169–76. doi:10.1007/s11262-006-0050-3. PMC 1892610. PMID 17143722.
  5. Cornu TI, de la Torre JC (2001). "RING finger Z protein of lymphocytic choriomeningitis virus (LCMV) inhibits transcription and RNA replication of an LCMV S-segment minigenome". J Virol. 75 (19): 9415–26. doi:10.1128/JVI.75.19.9415-9426.2001. PMC 114509. PMID 11533204.
  6. Djavani M, Lukashevich IS, Sanchez A, Nichol ST, Salvato MS (1997). "Completion of the Lassa fever virus sequence and identification of a RING finger open reading frame at the L RNA 5' End". Virology. 235 (2): 414–8. doi:10.1006/viro.1997.8722. PMID 9281522.
  7. Smelt SC, Borrow P, Kunz S, Cao W, Tishon A, Lewicki H; et al. (2001). "Differences in affinity of binding of lymphocytic choriomeningitis virus strains to the cellular receptor alpha-dystroglycan correlate with viral tropism and disease kinetics". J Virol. 75 (1): 448–57. doi:10.1128/JVI.75.1.448-457.2001. PMC 113937. PMID 11119613.
  8. Bowen MD, Rollin PE, Ksiazek TG, Hustad HL, Bausch DG, Demby AH; et al. (2000). "Genetic diversity among Lassa virus strains". J Virol. 74 (15): 6992–7004. PMC 112216. PMID 10888638.
  9. 9.0 9.1 "Wikipedia Natal multimammate mouse".
  10. 10.0 10.1 10.2 "Public Health Image Library (PHIL), Centers for Disease Control and Prevention".

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