West Nile virus (WNV) is a seasonal arbovirus geographically widespread in regions of Africa, Asia and the Middle East. In 1999, it was detected in New York City and from then on has spread westward and is now found in all continental states[1]. It was first isolated from a patient in the West Nile region of Uganda in 1937 [1]. In 2018 (as of Nov 13 2018), 2323 cases of WNV have been reported in the U.S.A. to the CDC. See here for an updated case distribution in North America. There is currently no human vaccine available for WNV. Prevention is through wearing repellent, taking steps in the home and sleeping under a net if travelling. Most cases are asymptomatic. Approximately, 1 in 5 people develop a fever and other symptoms, with 1 in 150 people developing a serious, occasionally fatal case. The disease is a zoonosis – spread primarily between birds (crows, jays, raptors) and Culex mosquitoes – with horses and humans acting as dead-end hosts [2]. There are several myths surrounding WNV transmission. Up until recently, it was believed that handling of live or dead infected birds can cause infection.


  1. Goddard LB, Roth AE, Reisen WK, Scott TW. Vector competence of California mosquitoes for West Nile virus. Emerging infectious diseases. 2002 Dec;8(12):1385. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738502/

  2. Hayes EB, Komar N, Nasci RS, Montgomery SP, O'Leary DR, Campbell GL. Epidemiology and transmission dynamics of West Nile virus disease. Emerging infectious diseases. 2005 Aug;11(8):1167. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320478/