West Nile Virus Surveillance

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 during WNV season. Data from previous years is updated annually.

Supporting Resources

Provincial Trends



The graphs below have the following common features including: interactive legend, a scrollbar (when applicable) to navigate the data, zoom in, zoom out, download graph data, annotate graph and export graph as an image.

Other Arboviruses and Mosquito Species of Interest

As of September 5, 2019 there has been five reported equine cases of Eastern Equine Encephalitis (EEEV), with two each from LGL and SUD, and one from THB. There have been no reports of EEEV positive mosquito pools or human cases.

  • 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 August 31, 2019):

  • One human case reported in British Columbia
  • Ten positive mosquito pools in Quebec and six in Manitoba

WNV United States (January 1 to September 17, 2019):

  • The Centers for Disease Control and Prevention (CDC) has reported 468 human cases of WNV, with 46 states and the District of Columbia reporting WNV activity (people, birds, or mosquitoes).
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Enteric, Zoonotic and Vector-Borne Diseases


Updated 18 Sep 2019