West Nile Virus disease (WNV) is a zoonotic disease caused by West Nile Virus (WNV). West Nile virus (WNV) is a kind of encephalitis virus, which is the main reservoir in birds. Horses, mosquitoes and humans can all be its infectious hosts. The onset time of human infection is about 33 days later than that of birds. The mosquito breeding season is the high incidence season of the disease. West Nile virus infection occurs from June to November, with the peak in late August. All people who have not been exposed to West Nile virus are susceptible, and the elderly and the immune system are prone to disease and fatality is high.

West Nile virus belongs to the flavivirus genus of the flaviviridae family, the same genus as Japanese encephalitis, St. Louis encephalitis, yellow fever, dengue fever, and hepatitis C. There is a capsule membrane, single-stranded linear ribonucleic acid, RNA is a positive strand, about 10,000 to 11,000 base pairs, and it is infectious. Under electron microscope, the virus was medium size, with a diameter of 21nm ~ 60nm, and was sensitive to organic solvents and ultraviolet rays.