Mosquito-borne disease surveillance: Seasonal update: Vector-borne disease surveillance in Canada

Vectors, such as mosquitoes, spread diseases between humans or from animals to humans, usually by biting. Diseases spread by vectors are called vector-borne diseases. Find out how we monitor mosquito-borne diseases in Canada.

  • Last updated: 2023-11-20

Update schedule

We update this page every other Monday during the typical transmission season (approximately July to October). It was last updated on November 20, 2023 at 2 pm ET. Data as of November 5, 2023 (epidemiological week 45).

On this page

The Public Health Agency of Canada (PHAC) monitors mosquito-borne diseases throughout the year using a One Health approach. Mosquitoes are usually active in Canada between spring and fall. This update provides the most recent data for humans, mosquito pools, and other animals reported to PHAC. There is no equivalent seasonal updates for tick-borne diseases.

About One Health

PHAC uses a One Health approach, which recognizes the interdependence of human health, animal health and their shared environment. Vector-borne diseases are increasing due to warmer temperatures and range expansion of mosquito and tick habitats.

West Nile virus (WNV)

Figure 1. Map of WNV human cases, positive mosquito pools, and infections in horses and dead wild birds in Canada, by reporting province or territory

19 cases of WNV have been reported among who became infected in Canada.

Figure 1 - Text description

case of WNV been reported among residents of Canada who became infected in Canada.
case of WNV been reported in residents of Canada who became infected while traveling outside of Canada.

Table 1. WNV human cases, positive mosquito pools, and infections in horses and dead wild birds in Canada, by reporting province or territory

This table does not include residents of Canada who became infected while traveling outside of Canada. WNV infections are attributed to the province or territory reporting them, which is not necessarily where the infection occurred.

Reporting province or territory Human cases Positive mosquito pools Positive horses Positive dead wild birds
About the data
  • Surveillance of mosquitoes, dead wild birds and horses for West Nile virus varies by province or territory.
  • N/A means that the province or territory doesn’t conduct this type of surveillance.
  • 0 means that no cases or infections were reported to PHAC during the most recent surveillance year.
  • Surveillance counts may vary from those on provincial or territorial websites. We’ll update our data as our reporting partners share new information with us.

Clinical cases, asymptomatic cases and severe outcomes

Clinical cases of WNV can present with symptoms that range from mild to severe. Asymptomatic cases are those in which the patient has no symptoms and has typically been identified through routine testing of donated blood.

Clinical cases
  • neurological
  • non-neurological
  • unspecified clinical

Asymptomatic cases

About these data tiles

Cases are classified using the clinical and lab criteria in the WNV national case definition. Deaths are determined at the local or provincial or territorial level, so there may be differences in how they’re classified or investigated.

  • A case that meets both the lab and the clinical criteria may be classified as:
    • West Nile neurological syndrome: The patient has severe disease that affects the central nervous system (for example, dangerous inflammation of the brain or spinal cord)
    • West Nile non-neurological syndrome: The patient has less severe or flu-like symptoms such as fever, body aches, headache or nausea
    • West Nile unspecified: The patient meets clinical criteria but no classification has been specified
  • A case that meets the lab criteria but doesn’t meet any of the clinical criteria is classified as a West Nile asymptomatic infection.
  • A case is recorded as a death when WNV was a direct or contributing cause of the death.

Eastern equine encephalitis virus (EEEV)

  • No cases of EEEV in horses have been reported.
  • No EEEV infections in humans have been reported.

California serogroup viruses (CSGV)

  • No CSGV positive mosquito pools have been reported.
  • 1 CSGV infection in humans has been reported.

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