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West Nile Virus (WNV) is a Flavivirus that can infect and cause disease in people, birds, horses, and many other animals. It is transmitted by the bites of infected mosquitoes (at least 50 species worldwide). The virus multiplies in the tissues of infected birds, circulates in the blood, and may be picked up by mosquitoes taking blood meals from these birds. These infected mosquitoes may then transmit the virus when they fly to another bird or animal and feed again. Although wild birds are the usual host animals infected by WNV, the virus also may infect amphibians, domestic poultry, domestic mammals (particularly horses), humans, apes, and monkeys. Please visit the Public Health Agency of Canada website for human disease information.


The CWHC coordinated a massive national surveillance project to monitor WNV in birds across Canada from 199X until 200X. Since then, monitoring has continued as part of our ongoing surveillance efforts, with approximately 300 birds per year being tested for WNV since 2009. The CWHC works with governmental agencies and other organizations, such as the World Organization for Animal Health (OIE) to report occurrence of WNV in a timely fashion.