West Nile Fever is seen in Africa, southern Europe, the Middle East, and in some parts of Asia. Lately West Nile Fever is spreading in other parts of the world, e.g. in the year 1999, the disease was introduced in New York City and spreading in other parts of the United States subsequently, especially in many of the northeastern states of United States. The West Nile Fever, after introduction in the New York City has caused several cases of aseptic meningitis and/or encephalitis among humans. The West Nile Fever virus is also causingserious problems among crows, exotic zoo birds, and other birds in the northeastern states of United States. The virus is also spreading and already spread to neighbouring Canada and Mexico. In the United States approximately 1000–3000 cases of encephalitis occurs (due to West Nile Fever virus) annually with approximately 100–300 deaths.

What is the causative agent of West Nile Fever?

West Nile Fever is caused by West Nile virus. The West Nile Fever virus belongs to phylogenetic group of flaviviruses, the same group of virus which cause St. Louis encephalitis and Japanese encephalitis, Murray Valley fever and Rocio fever.

How West Nile Fever is transmitted?

The West Nile Fever virus is transmitted by the bites of Culex mosquitoes in Africa, the Middle East, southern Europe, and Asia, (in the United States Culex pipiens is the major vector of West Nile Fever virus, although several other species of culex mosquitos are involved). Blue jays and crows acts as amplifiers of the West Nile Fever virus.

West Nile Fever virus can also be transmitted by organ transplantation and blood transfusion and screening of blood and organ donors by nucleic acid–based tests (by Nucleic acid amplification testing) should be performed to prevent transmission of West Nile Fever virus by organ transplantation and blood transfusion.

What are the symptoms of West Nile Fever?

Fever with generalized bofypain is a major symptom of West Nile Fever. The fever of West Nile Fever is different from other viral fevers by appearance (frequent) of a maculopapular rash on the trunk and lymphadenopathy. Headache, pain in the eyes, sore throat, nausea and vomiting, arthralgia (not arthritis) are also commonly seen in West Nile Fever. In Africa the virus (West Nile Fever virus) is implicated to cause severe and fatal hepatic necrosis. West Nile Fever virus may also cause subclinical infection (does not produce any symptom).

How West Nile Fever is treated?

The treatment of West Nile Fever mainly symptomatic and complications should be managed as they arise. Fever should be treated with antipyretic medication and general support given with adequate hydration and maintenance of adequate nutrition.

What are the complications of West Nile Fever virus infection?

Approximately 1% of the infections with West Nile Fever virus results in involvement of CNS (central nervous system) such as encephalitis. If encephalitis occurs the death rate is high even in developed countries (approximately 10% in United States). Complications and severity of complications are more among elderly persons, diabetics, and patients with previous CNS complications.

Milder complications include tremor, slight abnormalities in motor skills, and loss of executive functions.

Immunosuppressed patients (such as HIV infected persons and recipients of immunosuppressive therapy) may have more fulminant courses or develop persistent CNS infection.