West Nile Virus Mira J. Leslie State Public Health Veterinarian Washington State Department of Health Epidemiology of the North American outbreak

Washington State Department of Health Learning Objective West Nile virus is established in North America. The magnitude of the ongoing WNV outbreak is extraordinary and our knowledge is incomplete. Definitions:   Arbovirus = arthropod-borne virus Epizootic = epidemic in animals

Washington State Department of Health Do you remember when? Encephalitis- NYC 1999 SLE cases reported in Queens Active ph surveillance identified additional cases of encephalitis Causative agent unknown in many cases

Washington State Department of Health Bronx Zoo Zoo collection birds and birds in community (crows) dying. Veterinary pathologist pursued testing..West Nile virus isolated for the first time in Western Hemisphere.

Washington State Department of Health Initial outbreak

Washington State Department of Health West Nile virus: history 1937: First identified (human illness) West Nile district of Uganda ’s: Mild disease/ meningoencephalitis Middle East and Africa 1996 – 1999: Severe neurologic disease in Romania, Israel, Russia June 10, 323BC: Alexander the Great died in Babylon. ( htm)

Washington State Department of Health West Nile Virus- the organism Davis CT, Beasley DWC, Guzman H, Raj P, D’Anton M, Novak RJ, et al. Genetic variation among temporally and geographically distinct West Nile virus isolates, United States, 2001, Emerg Infect Dis 2003 Nov

Washington State Department of Health History of Arbovirus Outbreaks in North America YearVirus# neuro cases (approx) # deaths (approx) CFR 1933SLE % 1975SLE % 2003WN % CDC data

Washington State Department of Health Distribution of WNV activity,

Washington State Department of Health West Nile Virus, Human Cases 2003 epicenter 2002 epicenter

Washington State Department of Health West Nile Virus in the US How did it get here? Possible Pathways of Introduction Infected human host Human-transported vertebrate host   Legal   Illegal Human-transported vector(s) Storm-transported vertebrate host (bird) Intentional introduction (terrorist event)- not

Washington State Department of Health West Nile virus – transmission cycle Incidental hosts Vector mosquito Reservoir host -birds

Washington State Department of Health Mosquitoes: WNV vectors Mosquitoes: WNV vectors 37 species of native mosquitoes have tested positive in the U.S Some mosquitoes are more competent vectors than others. Environmental factors including climate play a role. Culex species including Culex tarsalis in the west are principal arbovirus vectors.

Washington State Department of Health Birds: WNV reservoir hosts More than 225 species have been reported to be infected with WNV. Crows and jays predominate with a high fatality rate. Variable experiences: Chicago vs. Connecticut.

Washington State Department of Health Learning about avian reservoirs of WNV Most competent reservoirs: Blue jay, Common grackle, House finch, American crow, House sparrow Transmission routes: mosquitoes, ingestion, and bird-bird contact. Some birds have persistent infection in many organs including skin. Komar et al. Experimental Infection of North American birds with the New York 99 strain of West Nile Virus, Emerg Infect Dis, Vol 9, No. 3, March 2003

Washington State Department of Health Dead birds as early indicators of WNV activity

Washington State Department of Health Horses In 2002, an intense epizootic of equine WNV infection occurred (> 14,500 reported cases). Two new vaccines are licensed for use in horses. Horses do not develop sufficient viremia to amplify the virus.

Washington State Department of Health In addition to humans,bugs, birds, and horses Bats Squirrels, Chipmunk Skunk; Rabbit Goat, sheep, llama, deer… Zoo animals Harbor seal (Non-human) Primates Farmed Alligators….

Washington State Department of Health West Nile infection, U.S., 2003 Human illness: 9862 Fatality: 264 Corvid ( crow, jay ): 10,200 Other bird: 1866 Mosquito pools: 8384 Equine: 5145 Sentinel flocks: 1956 “Other” animals: 48 Canine: 37 Squirrel: 20 Feline: 1

Washington State Department of Health West Nile virus WNV activity, U.S. Jan 1- June 1, 2004: CasesStates Humans22 Birds13315 Mosq. pools 355 Equine73 Flocks553

Washington State Department of Health WNV Seasonality

Washington State Department of Health West Nile virus Surveillance/Response: Partnerships Public Health agencies Health care providers, laboratories Blood banks Wildlife agencies and orgs Zoos Entomologists, ecologists, cartographers Veterinarians, veterinary laboratories Universities The public, the media, and others ……….

Washington State Department of Health Arbonet, CDC   “Tracking the virus in real-time” Secure web-based reporting   Compiles data on humans, birds, mammals, sentinel flocks, mosquitoes, etc.   Humans recorded by syndrome and status   Real-time mapping- USGS Human cases, 2004

Washington State Department of Health Take home messages West Nile virus: Established ecological niche in North America WNV outbreaks are unpredictable and our understanding is rudimentary. Management: flexibility, coordination, partnerships Plan surge capacity.

Washington State Department of Health Who is this “human”? QUESTIONS?

Washington State Department of Health West Nile virus-important issues Laboratory testing   Public health labs,commercial labs   Veterinary labs   Test development Communications   Health Alert messaging   Prevention messaging   Strategies and target audiences