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Clinical and Laboratory Features of West Nile Virus Infection

In this small sample, outcomes were generally good, but movement disorders were common.

West Nile virus (WNV) can cause a nonspecific febrile illness, meningitis, encephalitis, or a poliomyelitis-like illness. In 2002, 4156 human cases of WNV infection were reported in 44 U.S. states; 284 (6.8%) of these patients died. As of August 29, 2003, 1602 cases and 29 deaths had been reported in 34 U.S. states (for the latest numbers, see the CDC website). For physicians and for the interests of public heath in general, it would be useful to identify clinical features unique to WNV infection. To prospectively identify the clinical and laboratory features and outcomes of the neurologic complications of WNV infection, researchers identified 39 patients who presented with suspected WNV infection in Louisiana between August 1 and September 2, 2002. These patients underwent a standardized assessment, and results of laboratory tests were recorded; surviving patients were reassessed 8 months later.

Sixteen patients (41%) had confirmed WNV infection (5 meningitis, 8 encephalitis, 2 acute flaccid paralysis [AFP], and 1 encephalitis plus AFP). Notably, 15 patients had movement disorders, including tremor, myoclonus, and parkinsonism. The 3 patients with AFP had parkinsonism and bowel and bladder dysfunction. Only one patient (who had West Nile encephalitis) died. All patients with meningitis and 5 of 7 surviving patients with encephalitis had favorable outcomes. However, the patients with AFP had persistent weakness and continued to be nonambulatory. Persistent fatigue, myalgias, and headaches were relatively common sequelae in all survivors.

Comment: This report expands our knowledge of the clinical spectrum of WNV infection in the U.S. The identification of movement disorders as a common feature is particularly useful. However, many of the other clinical findings that are described are not particularly informative, as they constitute one or more of the criteria used to define the relevant clinical syndromes. For example, knowing the percentage of patients with encephalitis who had behavioral or personality changes is not very useful because personality change is one of the diagnostic criteria for encephalitis. The relatively benign outcome of most patients in this series is surprising and differs from outcomes in previous reports (e.g., Ann Intern Med 2002; 137:173).

— Christina M. Marra, MD

Dr. Marra is Professor, Departments of Neurology and Medicine (Infectious Diseases), University of Washington, Seattle.

Published in Journal Watch Neurology September 25, 2003

Citation(s):

Sejvar JJ et al. Neurologic manifestations and outcome of West Nile virus infection. JAMA 2003 Jul 23/30; 290:511-5.

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