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Clinical manifestations and diagnosis of West Nile virus infection

Lyle R Petersen, MD, MPH
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


West Nile (WN) virus, a member of the Japanese encephalitis virus antigenic complex, can lead to a wide range of clinical symptoms from asymptomatic disease to severe meningitis and encephalitis.

The clinical manifestations and diagnosis of WN virus are discussed below. Topics that discuss the epidemiology and pathogenesis of this infection, as well as the treatment and prevention of WN virus, are found elsewhere. (See "Epidemiology and pathogenesis of West Nile virus infection" and "Treatment and prevention of West Nile virus infection".)


Approximately 25 percent of those infected with West Nile (WN) virus develop WN fever, and 1 out of 150 to 250 develop neuroinvasive disease. Increasing viral load and female gender may increase the risk of developing WN fever [1].

There are several risk factors for developing neuroinvasive disease. These include:

Age – Advancing age is by far the most important risk factor for neuroinvasive disease, particularly encephalitis [2,3].

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Literature review current through: Nov 2017. | This topic last updated: Apr 07, 2017.
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