The Ministry of Health and Long-Term Care (MOHLTC) updated data once per day regarding dead bird surveillance for West Nile virus (WNv) (dead crows are indicated as well as ravens in northern Ontario). This information is provided to the Public Health Branch by the Canadian Cooperative Wildlife Health Centre (CCWHC) laboratory which carries out the WNv testing on birds, supported by Health Canada. The reports include the date of finding the first WNv positive crow in a Health Unit as well as the date of the last WNv positive one found in the Health Unit.

It is important to note that the absence of positive bird findings after the last date does not imply that WNv is no longer in the local bird population. In order to accurately interpret the data, the following further explains the purpose of the sampling and the process.

The submission of birds to the CCWHC by public health units is based on the arrival time of birds in the Spring in each area of the province as established by the experience of the naturalists of the CCWHC. Each Health Unit is allotted a fixed number of submissions per week for WNv testing to maximize the resources of the CCWHC in covering the anticipated arrival of crows.

The sole purpose of bird surveillance is to establish whether or not the WNv is present in the Health Unit. This is key information required by the medical officer of health for each local health unit for purposes of decision making. The WNv bird surveillance is not intended as an ongoing monitoring of the status of bird health with respect to WNv.

Once it is established that WNv exists in the bird population within a local health unit, it is an appropriate assumption that WNv infection exists throughout the bird flocks in that jurisdiction. Once established, further bird testing is no longer deemed a necessary activity, and the CCWHC reserves the option to re-allot testing submissions to other areas within the Province which have not demonstrated WNv in their bird populations.

Below is a list of birds that have been confirmed or presumed positive for WNv in Ontario in 2002.

• Public Health Units
• Humans
• Mosquitoes
• Horses

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