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West Nile Virus surveillance
To learn more about how to use the features on this page, watch our introductory video.

West Nile Virus (WNV) is a vector-borne disease of public health importance in Ontario. Each week, we analyze provincial mosquito, human and weather data to produce a weekly vector surveillance report. Public health units provide us with mosquito and human data, and Environment Canada is our source for weather data. Updated case counts are available every Wednesday below. Data from previous years is updated annually.

For more information on the graphs, maps, and health unit codes, please read the West Nile Virus surveillance glossary and data caveats. If you have any questions, please contact

Surveillance Week 27 (July 1– July 7, 2018)

Provincial Trends

As of week 27 there have been zero reported (confirmed or probable) human WNV cases:

There has been one WNV positive mosquito pool:
WEC (1)

 Equine: No WNV equine cases have been reported for 2018.

Other arboviruses and mosquito species of interest

As of July 10, 2018 there have been no reports of horses or mosquitoes testing positive for Eastern Equine Encephalitis (EEEV).            

  • Culiseta melanura is an important mosquito vector in the transmission cycle of EEEV as it is responsible for amplifying the virus in the bird population.
  • Although large numbers of Cq. perturbans can be identified in Ontario, this species is not considered a competent vector species in the transmission of WNV due to the presence of a substantial salivary gland barrier (Sardelis et al. 2001).
Vector-borne disease activity in other jurisdictions   

WNV Canada (January 1 to June 30, 2018):

  • No humans cases, or WNV positive mosquito pools have been reported on the PHAC webpage.
WNV United States (January 1 to June 26, 2018):        
  • The Centers for Disease Control and Prevention (CDC) has reported 10 human cases of WNV, with 23 states reporting WNV activity (people, birds, or mosquitoes).​​​​​
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Page last updated: 2018-07-10 12:39 PM
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