People become infected with West Nile encephalitis from the bite of an infected mosquito. The virus is not transmitted from person to person. West Nile virus has been described in Africa, Europe, the Middle East, west and central Asia, Oceania, and most recently, North America. The incubation period (time it takes from getting the virus until symptoms are noticed) of a West Nile virus infection is usually five to fifteen days. Mild infections are common and include fever, headache and body aches, often with skin rash and swollen lymph glands.
Encephalitis occurs when the virus invades the central nervous system destroying the brain with accompanying inflammation. The symptoms include muscle weakness and paralysis, mild confusion and behavioural changes (which may be mistaken for hysteria), convulsions (fits) and deep coma.
There is no specific treatment for West Nile virus. Current management consists of treating the complications of the condition such as high fever and aches, some patients are left with severe paralysis, convulsions or raised intracranial pressure.
The simplest preventative measure is to avoid bites from the mosquitoes that carry the virus. This involves wearing long sleeves and trousers, especially during the evening. For further protection use an insect spray containing at least 30 per cent DEET (N,N-diethyl-3methlybenzamide) and sleep under bed-nets.