West Nile virus

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Meninges of the brain	Mosquito, adult	Mosquito, adult feeding on the skin	Mosquito, egg raft
Mosquito, pupa

Mild disease, generally called West Nile fever, has some or all of the following symptoms:

• Fever
• Headache
• Back pain
• Muscle aches
• Lack of appetite
• Sore throat
• Nausea
• Vomiting
• Abdominal pain
• Diarrhea

These symptoms usually last for 3 to 6 days.

With more severe disease, the following symptoms can also be seen and require prompt attention:

• Muscle weakness
• Stiff neck
• Confusion or change in clarity of thinking
• Loss of consciousness

Signs of West Nile virus infection are similar to those of other viral infections. There is nothing that can be found on physical examination to diagnose West Nile virus infection.

A rash is present in 20-50% of patients. True muscle weakness in the presence of other related symptoms is suggestive of West Nile virus infection.

Tests to diagnose West Nile virus include:

• CBC
• Lumbar puncture and cerebrospinal fluid (CSF) testing
• Head CT scan
• Head MRI scan

However, the most accurate way to diagnose this infection is a serology test, which checks a blood or CSF sample for antibodies against the virus.

Rarely, a sample of blood or CSF may be sent to a lab to be cultured to look for the presence of West Nile virus. The virus can also be identified in body fluids using a technique called polymerase chain reaction (PCR). However, these methods can provide false negative results.

Review Date: 09/25/2006
Reviewed By: Charlotte Grayson, MD, Private Practice specializing in Internal Medicine and Infectious Disease, Smyrna, GA. Review provided by VeriMed Healthcare Network.