This week on virus of the week is West Nile Virus, another single stranded RNA virus belonging to the flavivirus family! Learn more about other dengue and tick-bourne encephalitis virus!



  • WNV was first isolated from a febrile patient from the West Nile district of Northern Uganda in 1937, (Smithburn et al., 1940).
  • Following naming conventions of the time it was called WNV.

Hosts: What carries WNV?

  • Natural hosts of WNV are mosquitoes and birds, (Jerzak et al., 2005).
  • Culex mosquitoes are particularly important for WNV transmission into humans!
  • Humans are ‘dead end hosts’ – meaning we don’t transmit back to mosquitoes.

Cell Tropism: Which cells can WNV infect?

Vector: What transmits WNV to humans?

  • Culex mosquitoes transmit to humans.
  • This includes: Culex pipiens, C. restuans, C. salinarius, C. quinquefasciatus, C. nigripalpus, C. erraticus and C. tarsalis.

Pathology: What does it do to us?

  • 80 % of infections are asymptomatic.
  • The majority of symptomatic patients experience a weeklong fever.
  • West Nile neuroinvasive disease (WNND) occurs in less than 1 % of infections.

It describes multiple syndromes:

  • West Nile meningitis (WNM)
  • West Nile encephalitis (WNE)
  • West Nile poliomyelitis (WNP)

Did you know?

Men are more likely to experience WNND!


  • Brown, A. N., Kent, K. A., Bennett, C. J., & Bernard, K. A. (2007). Tissue tropism and neuroinvasion of West Nile virus do not differ for two mouse strains with different survival rates. Virology, 368(2),422–430.
  • Byas, A. D., & Ebel, G. D. (2020). Comparative pathology of West Nile Virus in humans and non-human animals. Pathogens, 9(1).
  • Jerzak, G., Bernard, K. A., Kramer, L. D., & Ebel, G. D. (2005). Genetic variation in West Nile virus from naturally infected mosquitoes and birds suggests quasispecies structure and strong purifying selection. The Journal of General Virology, 86(Pt 8), 2175–2183.
  • Kilpatrick, A. M., LaDeau, S. L., & Marra, P. P. (2007). Ecology of West Nile Virus Transmission and Its Impact on Birds in the Western Hemisphere. The Auk, 124(4), 1121–1136.
  • Petersen, L. R., Brault, A. C., & Nasci, R. S. (2013). West Nile virus: review of the literature. JAMA, 310(3), 308–315.
  • Smithburn, K. C., Hughes, T. P., & Burke, A. (1940). A neurotropic virus isolated from the blood of a native of Uganda. The American Journal of Tropical Medicine, 20, 471–497.