West Nile Virus (WNV)
Lyme Disease (LD)
Eastern Equine Encephalitis Virus (EEEV)

West Nile Virus (WNV) is a mosquito-borne disease that can cause mild to serious symptoms, but is rarely fatal.  In 2002, the first cases of WNV were reported in Ontario. In response to the emergence of WNV over the last decade, Ontario public health units conduct weekly mosquito surveillance in an effort to identify areas of risk. Public Health Ontario (PHO) analyzes provincial mosquito, human and weather data.  Mosquito and human data is provided by the local public health units and the weather data is extracted from Environment Canada. PHO produces a weekly vector surveillance report giving both the provincial and local perspective.

PHO uses accumulated degree data to assist in assessing risk of contracting WNV, since weather is a risk factor for WNV. The accumulated degree days will help to determine the level of risk. However, the level of mosquito and human activity must also be considered in the risk analysis. For example, a public health unit with a large number of accumulated degree days with no activity would have a lower risk than one that has moderate accumulated degree days but has had numerous positive mosquito pools.  

Weekly Vector-Borne Disease Surveillance Reports

Weekly Vector Surveillance Report - Week 42
Weekly Vector Surveillance Report - Week 41
Weekly Vector Surveillance Report - Week 40
Weekly Vector Surveillance Report - Week 39
Weekly Vector Surveillance Report - Week 38
Weekly Vector Surveillance Report - Week 37
Weekly Vector Surveillance Report - Week 36
Weekly Vector Surveillance Report - Week 35
Weekly Vector Surveillance Report - Week 34
Weekly Vector Surveillance Report - Week 33
Weekly Vector Surveillance Report - Week 32
Weekly Vector Surveillance Report - Week 31
Weekly Vector Surveillance Report - Week 30
Weekly Vector Surveillance Report - Week 29
Weekly Vector Surveillance Report - Week 28
Weekly Vector Surveillance Report - Week 27
Weekly Vector Surveillance Report - Week 26

Accumulated Degree Days
Definitions for Vector Surveillance Reports

Vector-Borne Disease 2011 Summary Report

This report provides an overview of Ontario’s 2011 vector-borne disease season based on surveillance data.  The major vector-borne diseases of public health importance in Ontario are West Nile Virus (WNV), Eastern Equine Encephalitis Virus (EEEV) and Lyme disease (LD).

Eastern Equine Encephalitis Virus (EEEV) has been present in the horse population in Ontario since 1938.  In the last few years, surveillance data from health units and First Nations Inuit Health Branch has detected the virus in the mosquito population. Although the risk is still low in Ontario, and there has never been a human case of EEEV reported in the province, enhanced surveillance for the virus was implemented due to the increased activity (equines and mosquitoes) in the surrounding jurisdictions.