West Nile virus prognosis linked to symptoms: neurological manifestations.(Clinical Rounds)

The poliomyelitis-like syndrome that is sometimes associated with West Nile virus is linked with a poor long-term outcome and may be irreversible, researchers reported in the Journal of the American Medical Association in two articles that coincided with an explosive summer spread of disease activity across the United States.

Researchers also noted that dyskinesias--including tremor, myoclonus, and parkinsonism--appear to be very frequent manifestations of the disease, and that these symptoms often resolve.

Movement disorders and a poliomyelitis-like acute flaccid paralysis were not well-recognized sequelae of West Nile virus early in the course of the epidemic that first struck New York City in 1999. But small studies are starting to clarify the clinical picture of disease presentations in the United States and Canada, even as more cases of the mosquito-borne disease are reported.

As of Aug. 14, 446 patients from 24 states were confirmed ill and 10 patients had died from West Nile virus. Viral activity had spread to 42 states, sparing only the far West, Hawaii, and Alaska.

Last year's explosion of cases--4,156 cases and nearly 300 deaths--provided a better understanding of the presenting symptoms, disease course, and prognosis of patients infected with West Nile virus.

Most patients exposed to the virus remain asymptomatic; others have only a mild, flu-like illness lasting 3-6 days and marked by malaise, anorexia, gastrointestinal symptoms, eye pain, headache, and myalgia. Lymphadenopathy and an erythematous macular, papular, or morbilli-form rash were commonly reported in earlier outbreaks, but are evidently not common symptoms in the current epidemic.

Fever, severe weakness, gastrointestinal symptoms, headache, and movement disorders are often associated with severe neurologic disease, which strikes fewer than 1% of infected individuals. Destruction of the spinal anterior horn cells may cause acute flaccid paralysis (AFP), ...