Michael A. Drebot, PhD, Chief, Viral Zoonoses, Zoonotic Diseases and Special Pathogens, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
Harvey Artsob, PhD, Director, Zoonotic Diseases and Special Pathogens, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.

Since its introduction into North America in 1999, West Nile virus (WNV) has rapidly expanded its range across the continent. There is evidence that it has moved into the Caribbean and South and Central America. The virus has significantly affected public health, causing more than 20,000 cases of associated illness and resulting in the largest WNV epidemic ever recorded. Although neuroinvasive disease occurs in less than 1% of infections, the risk for encephalitis and other neurological illnesses increases with age. Currently there is no specific therapy for the treatment of WNV-associated disease and a vaccine is not yet available. Decreasing the risk of virus exposure requires seasonal preventative and control measures.
Key Words: West Nile virus, epidemiology, diagnosis, neurological illness, disease prevention.