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West Nile Virus surveillance
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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. Until June 2016, weekly West Nile Virus surveillance reports were available in PDF form. This data, from 2002 year to the most recent surveillance week, is now available in the graphs below.

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 25 (June 18 – June 24, 2017)

Provincial Trends

  • As of week 25, there are no reports of WNV positive mosquito pools or human cases in Ontario.
  • Equine: Currently, no horses have been reported with WNV.
  • The majority of mosquitoes species were captured in low numbers across Ontario. The Coquillettidia genus is not a major vector of WNV in Ontario, and was caught in relatively low numbers, but can be a biting nuisance. The number of Cx. pipiens/restuans that are being captured is low across province.
Other arboviruses and mosquito species of interest
There have been no reports of mosquitoes, or horses, 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. This species was reported in relatively low numbers in week 25.
  • 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 27, 2017):
  • Human cases have not been reported.
  • Mosquito pools have not been reported.
WNV United States (January 1 to June 27, 2017):        
  • The Centers for Disease Control and Prevention (CDC) has not reported any WNV activity for 2017 .
Uncontrolled print copy. Valid only on day of Print: [date]
Page updated on [date/time] 27/06/2017 11:15 AM
© , Ontario Agency for Health Protection and Promotion