West Nile virus Health Article

Signs and tests

Signs of West Nile virus infection are similar to those of other viral infections. There may be no specific findings on a physical examination to diagnose West Nile virus infection.

About 20 - 50% of patients may have a rash. Muscle weakness with other related symptoms are signs of a West Nile virus infection.

Tests to diagnose West Nile virus include:

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

The most accurate way to diagnose this infection is with 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 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 and are not commonly used.

Treatment

Because this illness is not caused by bacteria, antibiotics do not help treat West Nile virus infection. Standard hospital care may help decrease the risk of complications in severe illness.

Research trials are under way to determine whether ribavirin, an antiviral drug used to treat hepatitis C, may be helpful.

Expectations (prognosis)

In general, the likely outcome of a mild West Nile virus infection is excellent.

For patients with severe cases of West Nile virus infection, the outlook is more uncertain. West Nile encephalitis or meningitis may lead to brain damage and death. Approximately 10% of patients with brain inflammation do not survive.

Complications

Complications from mild West Nile virus infection are extremely rare.

Complications from severe West Nile virus infection include:

• Permanent brain damage
• Permanent muscle weakness (sometimes similar to polio)
• Death