Public Health Ontario Launches New Ontario Vector-Borne Disease Tool

Announcements

5 June 2025

Public Health Ontario’s (PHO) new Ontario Vector-Borne Disease Tool offers comprehensive surveillance data on vector-borne diseases (VBDs) in Ontario, presenting data from multiple surveillance systems and partners. The VBD Tool consolidates data from several existing PHO resources into a single platform, offering a modern, intuitive experience with enhanced geographic functionality and interactive data visualizations.

Key features and uses of the tool:

  • Monitor trends: Track weekly and year-to-date case counts for all reportable vector-borne diseases, including West Nile virus illness, Lyme disease, anaplasmosis, babesiosis, Powassan virus infection, at both the provincial and public health unit levels.
  • Geographic analysis: Visualize mosquito and tick surveillance data, including species distribution and positive test results, using interactive maps with customizable layers.
  • Risk assessment: Access interactive blacklegged tick established risk area maps, to better support public health professionals and clinicians in their management and case investigations of tick-borne diseases.
  • More frequent updates: Data are available from 2014 to present. Weekly updates from May through October for human case and mosquito data, will support enhanced surveillance during peak vector activity.

What’s included in the tool:

As a centralized resource of VBD surveillance data, the following PHO resources have been discontinued, with information integrated into the new Ontario Vector-Borne Disease Tool:

  • West Nile Virus Surveillance Tool
  • Ontario Blacklegged Tick Established Risk Areas maps

Tab

Description

Vectors

Overview – Ontario

Summary of current VBD activity in Ontario, including year-to-date and most recent weekly case counts

Anaplasmosis, Babesiosis, Lyme disease, Powassan virus infection, West Nile virus illness

Overview – PHU

Case counts and rates by public health unit (PHU), including data on positive mosquito pools

Anaplasmosis, Babesiosis, Lyme disease, Powassan virus infection, West Nile virus illness

BLT Risk Areas

Interactive map showing the expansion of blacklegged tick populations since 2015 using active tick surveillance data

Blacklegged ticks (Ixodes scapularis)

Mosquito Traps

Locations and species distribution data from mosquito traps

Culex pipiens/Culex restuans, Aedes vexans, Coquillettidia perturbans, Ochlerotatus canadensis, and Ochlerotatus japonicus

Mosquito Species

Weekly average abundance of mosquito species

Culex pipiens/Culex restuans, Aedes vexans, Coquillettidia perturbans, Ochlerotatus canadensis, and Ochlerotatus japonicus

Lyme Disease, West Nile Virus illness Human case rates, positive mosquito pools, and percent positive ticks as of 2015 Lyme disease, West Nile virus illness
Anaplasmosis, Babesiosis, Powassan virus infection Human case rates since 2023 and percent positive ticks since 2015 Anaplasmosis, Babesiosis, Powassan virus infection
Eastern Equine Encephalitis Virus (EEEV) EEEV-positive mosquito pool locations (where detected) Eastern equine encephalitis virus

Ontario Blacklegged Tick Established Risk Areas

In 2025, most of the risk areas are in southern Ontario along the north shores of Lake Erie, Lake Ontario and the St. Lawrence River. There are also risk areas within the health unit boundaries of Northwestern and Thunder Bay. The current map has thirteen newly identified areas in six different PHUs: MSL (2), NIA (1), PEL (2), REN (3), SEH (3), and WAT (2).

It is important to note that while low, there is a possibility of encountering blacklegged ticks almost anywhere in the province, provided the habitat is suitable (e.g., wooded or brushy areas).

Where does data from the tool come from?

The data presented in the tool are sourced from multiple surveillance systems and partners:

  • Human vector-borne disease data: All VBD surveillance data are sourced from PHO’s Infectious Disease Trends in Ontario (IDTO) tool up to and including 2023. Data for 2024 and recent years are sourced from the integrated public health information system (iPHIS).
  • Tick data:
    • Blacklegged Tick established risk areas: Tick dragging data (active tick surveillance) are reported to PHO on an annual basis by the National Microbiology Laboratory (NML) at the Public Health Agency of Canada.
    • Percent positive: percent of blacklegged ticks collected through active surveillance (tick dragging) that tested positive for disease using PCR/RT-PCR testing, and results are reported to PHO.
  • Mosquito surveillance and testing: Maintained by PHO, includes mosquito identification and arbovirus testing for Eastern equine encephalitis virus and West Nile virus.

What can I do if I can’t find the information that I am looking for?

If you can’t find the information you are looking for, please email your questions to communicable.diseasecontrol@oahpp.ca.

We will also be offering an online demo of the tool. Check out our Events page for more details.

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Contact

Communications

communications@oahpp.ca

Published 5 June 2025