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Arboviral Encephalitides
West nile encephalitis
West Nile virus is an arthropod-borne virus (i.e an arbovirus) transmitted between birds by infected mosquitos. People become infected with the virus following the bite of an infected mosquito. The virus is not transmitted from person to person. There is no evidence that a person can get the virus from handling live or dead infected birds. However, it is still recommended that bare-handed contact with dead animals is avoided.
The incubation period 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 results when the virus invades the central nervous system destroying the brain substance with accompanying inflammation. The clinical features range from muscle weakness and paralysis; to mild confusion and behavioural changes (which may be mistaken for hysteria); and to convulsions (fits) and deep coma.
There is no specific treatment for West Nile virus. Current management consists of treating the complications of the disease 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 when the mosquito bites and avoiding areas where stagnant water can be found - mosquito larvae need still water to develop. For further protection use an insect spray containing at least thirty per cent DEET (N,N-diethyl-3methlybenzamide) and sleep under bed-nets.
West Nile virus (genus Flavivirus, family Flaviviridae) was first identified in 1937. It was subsequently shown to have a very wide area of distribution that includes most of Africa, southern Europe, the Middle East, and even parts of the Far East. In its natural cycle, the virus is transmitted primarily between birds by mosquitoes. Classically, West Nile virus causes a non-specific febrile illness, and until recently nervous system manifestations were considered a rarity. However, in recent years the epidemiology has changed with the virus spreading to new areas and causing different disease patterns. In 1996 there was an epidemic of West Nile encephalitis in Romania, and in 1999 the virus reached the United States for the first time with an outbreak in New York. Since then it has spread across the Eastern and Central American states, and in 2002 caused its largest outbreak, with more than six thousand cases and thirty deaths reported by September 2002.
Inheritance patterns
None.
Prenatal diagnosis
None.
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