Travel Health Information Sheets
West Nile Virus
West Nile Virus (WNV) is spread by mosquitoes that usually bite at night and is caused by a virus carried by birds. WNV is similar to the viruses that cause dengue fever, Japanese encephalitis and yellow fever.
WNV was first diagnosed in a woman from the West Nile district of Uganda in 1937. It is found in Africa, Asia, Australia and the Middle East, with occasional outbreaks and cases in parts of Europe, such as Albania, Greece and the Russian Federation. In 1999, WNV was reported in New York and spread rapidly through all states in the USA and then to Canada, Mexico, Central America and the Caribbean.
Most infected people (80%) do not feel ill or have very mild symptoms. Less than 20% of infected people have a mild, flu-like illness, with fever, headache, muscle aches and a red, bumpy rash.
Very rarely, a serious meningitis-like illness can develop. Symptoms include a stiff neck, confusion, seizures, paralysis or coma. This is unusual, but the severe type of WNV can be fatal or can cause long term disability and personality changes. Unfortunately, it is difficult to predict who will develop this more dangerous form, although older people may be more vulnerable.
WNV is extremely unusual in tourists and travellers. However, as most infected people only get mild symptoms, it may be under-recognised.
You are at risk if you get bitten by mosquitoes in countries where WNV is found. This is more likely if you spend a lot of time outside after dark, especially in spring, summer and early autumn.
You cannot usually catch WNV directly from another person. Very rarely WNV has spread via blood transfusions and transplants or from mother to her baby during pregnancy and breast feeding.
The mosquito that carries WNV bites after dark (from dusk to dawn). You should follow strict insect bite avoidance advice.
See your doctor if you have any symptoms, especially fever with a rash.
There is no specific treatment. If your symptoms are mild, they usually improve after a few weeks and you are unlikely to have any long term problems.
If your symptoms are more serious, you may have to be admitted to hospital and need intensive care treatment.
No - careful bite avoidance is the only way to avoid WNV infection.
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