West Nile virus (WNv)

West Nile virus (WNv) is a disease caused by the virus with the same name. It is spread to humans by mosquitoes that have fed on the blood of infected birds. Many people infected with West Nile virus have mild or no symptoms. People with weaker immune systems and people with chronic diseases are at greater risk for serious health effects from WNv such as meningitis, encephalitis and acute flaccid paralysis.

The Simcoe Muskoka District Health Unit conducts surveillance for WNv in our area by testing mosquito larvae and adults as well as dead birds. For more information about these surveillance activities, visit the West Nile virus section of the health unit's website.

When the number of cases of a disease is less than five for one or more years, it is health unit policy to combine the data for multiple years. There was zero to one case of WNv reported to Simcoe Muskoka District Health Unit each year between 2000 and 2008 for a total of two cases in that time period. West Nile virus is a rare disease both locally and provincially. 

• The Simcoe Muskoka incidence rate varied between 0 - 0.2 cases per 100,000 population every year between 2000 and 2008 (Data Sources: iPHIS; Population Estimates and Projections 2000-08, Ontario MOHLTC, Provincial Health Planning Database (PHPDB) Extracted March 2009).
• The Ontario incidence rate was 0.8 cases per 100,000 population in 2005 (Data Sources: iPHIS; Population Estimates 2005, Ontario MOHLTC, Provincial Health Planning Database (PHPDB) Extracted March 2009).