West Nile virus in USA

23 Jun 2017

In recent weeks Health Departments across the United States of America have begun reporting the detection of West Nile virus in mosquitoes. A small number of human and animal cases have also been reported. Many health departments are now reminding locals to practice bite-avoidance to reduce risk of being infected. States reporting infected mosquitoes are across the United States from California in the West to Pennsylvania in the East, and Minnesota in the North to Texas in the South.

Mosquito season across the USA varies depending on latitude, ranging from May-August in the north to February-November in the south: in Alaska mosquito season is short from June to July.

West Nile is transmitted by Culex mosquitoes which bite mainly from dusk to dawn. Most infections are mild and severe infection is rare.

West Nile Fever is rarely reported in travellers. Risk is greatest in those undertaking outdoor activities.

Advice to travellers

Travellers should avoid mosquito bites by covering up and using insect repellants when outdoors especially at dawn and dusk or when mosquitoes are biting.

Further information can be found on the Insect Bite Avoidance page.