How is West Nile virus transmitted?

Updated: Apr 02, 2018
  • Author: Jess D Salinas, Jr, MD; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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The West Nile virus is transmitted to humans by the bite of an infected mosquito. Typically, warm climates and the summer months provide an ideal environment for mosquitoes to breed. [2, 23] Multiple mosquito bites and greater exposure to environments with a large mosquito population increase the risk of infection. However, some cases have been linked to organ transplantation, breastfeeding, and (possibly) blood transfusions. [24]

A study by Paull et al indicated that drought is the main climate component that increases West Nile virus epidemics and that by the late 2040s, climate change–driven increases in drought severity could cause cases of the virus to triple in regions where human immunity to it is low. The investigators found some evidence that drought increases West Nile virus epidemics by altering the prevalence of mosquito infection, as opposed to increasing the number of mosquitoes. [25]

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