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West Nile virus prognosis linked to symptoms: neurological manifestations.

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), presenting as asymmetric limb weakness, hypoflexia or areflexia, and acute bowel or bladder dysfunction that may appear without signs of meningoencephalitis.

Federal researchers noted that "substantial morbidity may follow hospitalization for West Nile virus," especially among patients with AFP (JAMA 290[4]:524-28, 2003).

"Patients with AFP due to the poliomyelitis-like syndrome have very limited recovery," wrote Dr. Lyle R. Petersen of the CDC and his associates at the U.S. Public Health Service and the Health and Human Services Department.

A companion study confirmed those conclusions in a close look at 16 patients who were followed prospectively in St. Tammany Parish, La., after presenting with symptoms in August 2002 (JAMA 290[4]:511-15).

One patient died 2.5 months after being diagnosed, having never emerged from a coma. Among the remaining 15, 10 reported persistent fatigue; 4, persistent cognitive defects; and 3, persistent myalgias 8 months after falling ill. Parkinsonism persisted in 5 of 11 affected patients.

The five patients with West Nile meningitis were younger than those with West Nile encephalitis (median ages 35 and 70, respectively), and they fared better. No patient with West Nile meningitis had neurologic deficits during follow-up examinations 8 months after diagnosis, said Dr James J. Sevjar of the CDC and associates.

The three patients with AFP had the lowest follow-up function scores, showing no improvement in limb weakness after 8 months. All three required use of wheelchairs and "described continuing difficulties with daily activities, such as grooming, housekeeping, and mobility."

Some of the Louisiana patients fared better than patients who were followed in previous studies. Seven of 10 who were previously employed had returned to work within 4 months. Good outcomes were reported in five of seven patients with severe encephalitis, including some of those who appeared gravely ill at onset.
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Title Annotation:Clinical Rounds
Author:Bates, Betsy
Publication:OB GYN News
Date:Sep 1, 2003
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