West Nile virus – History

The West Nile virus (WNV) was first isolated in 1937 in the West Nile district of Uganda. Since then, there have been outbreaks in Egypt, Israel, South Africa, and in parts of Europe, Asia and North America.

• The first recorded outbreak in North America happened in New York City in 1999.

No one knows for sure how the virus made its way to North America. There are many theories, including one that suggests the virus arrived on this continent through an infected migratory or imported bird, or through an infected mosquito that was transported to North America by accident.

The first reports of WNV activity in Canada came in August 2001, when the virus was found in dead birds and mosquito pools in southern Ontario. Canada had its first confirmed human cases in 2002, after people tested positive for West Nile virus in parts of Quebec and Ontario.

The virus was also found in birds, horses or mosquitoes in Nova Scotia, Quebec, Ontario, Manitoba and Saskatchewan. In Alberta the first infected bird was confirmed on July 9, 2003. The first human case was reported on August 12, 2003. In total, 275 human cases were reported that year.

• During 2003, more than 10,000 people in North America became ill after being infected with WNV, and 241 individuals died.

See Evidence in Alberta for Alberta West Nile virus statistics since 2003.