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West Nile Virus Infection in United States (Update)

21 Sep 2012

The ongoing outbreak of West Nile virus infection is now considered to be one of the worst ever to affect the US. New human infections and related deaths have brought the total to 3142 cases and 134 deaths. Of those, 1630 (52%) have been classified as neuroinvasive disease.

The only two states not reporting West Nile virus in either humans, animals or mosquitoes are Alaska and Hawaii. Two thirds of the human cases have been reported from 7 states: California, Louisaina, Michigan, Mississippi, Oklahoma, South Dakota and Texas. Almost 40% of all cases have been reported from Texas.

Advice for Travellers

West Nile virus infection is transmitted by Culex mosquitoes which bite mainly from dusk to dawn. Reservoir hosts are usually birds. Most infections are asymptomatic and severe infection is rare. West Nile virus infection is rarely reported in travellers. Risk is greatest in those undertaking outdoor activities. Travellers should take precautions to prevent mosquito bites especially during summer months.