West Nile virus is an illness that spreads from mosquitoes to humans. A mosquito becomes infected when it feeds on the blood of a bird that is carrying West Nile virus. About 2 weeks later, the mosquito is capable of spreading the virus to people and animals while biting for a blood meal. The virus is not spread from person to person, and cannot be spread directly from infected animals, such as birds, horses, or pets to people.
West Nile virus originated in the West Nile region of Uganda in 1937, and for decades it was confined to Africa, the Indian subcontinent, and parts of the Middle East and Europe. In 1999, it was detected in New York City, where 7 people died from it. Canada had its first confirmed infection in a bird in 2001. In 2002, the first confirmed human case of West Nile virus was reported in Ontario.
By 2003, West Nile virus had spread to 8 Canadian provinces and 1 territory: Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, Saskatchewan, Alberta, British Columbia, and the Yukon Territory. More than 1,400 Canadians were infected that year. Since then, there have been West Nile cases every year - the virus's continuing spread indicates that it is probably here to stay. Every year, the Public Health Agency of Canada (PHAC) publishes weekly reports during West Nile virus season on West Nile virus activity in Canada.
West Nile virus affects the central nervous system, and infection usually results in mild flu-like symptoms or no symptoms at all. However, in severe cases, infection with West Nile virus can be fatal. Affected provinces have developed aggressive strategies to tackle the problem, including surveillance programs to track the location and numbers of infected mosquitoes and birds.