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TUESDAY, July 22, 2003 (HealthDayNews) -- While most people who fall sick with the West Nile virus generally can expect a full recovery, some may suffer long-term and perhaps permanent movement problems, new research says.
The study, by scientists at the U.S. Centers for Disease Control and Prevention (CDC) and their colleagues, followed 16 confirmed cases of the mosquito-borne infection that surfaced in St. Tammany Parish, La., last summer. One patient died, but most of the rest regained full or essentially full function, returned to work and resumed normal lives.
For a few, however, the infection left a lasting legacy of weak limbs, tremors, serious muscle ticks and other motor trouble. In that way, West Nile virus resembles other emerging microbes that attack the nervous system.
"We're getting a sense that persistent motor problems can be seen with a number of viruses," says study author Dr. James Sejvar, a CDC West Nile expert.
Among these germs are Japanese encephalitis, a mosquito-borne pathogen related to West Nile that's the leading cause of encephalitis in Asia, and Nipah virus, another Asian organism.
As of July 18, the CDC had received reports of seven human cases of West Nile infection this year in four states: Alabama, Minnesota, South Carolina and Texas.
Last year was a breakout for West Nile in the United States: 4,156 people developed confirmed infections and 284 died of the disease, according to the CDC. It was by far the highest caseload since the virus appeared in this country in 1999. Experts believe only one in 100 infected people develop symptoms.
Since its U.S. arrival in New York City, the pathogen has marched steadily westward. Its range now extends from coast to coast. Scientists last year determined that West Nile could spread through blood transfusions and organ transplants. They also documented the first case of a mother passing the infection to her infant by nursing.
Earlier this month, Ohio scientists reported in the journal Neurology on 23 West Nile patients treated at the Cleveland Clinic. Half of people there with the infection had either brain or spinal cord inflammation accompanied by acute flaccid paralysis, or limb weakness.
The latest study, which appears in the July 23/30 issue of the Journal of the American Medical Association, offers a similar picture.
Led by Sejvar, of the CDC's division of viral and rickettsial diseases, the researchers analyzed 16 confirmed cases of West Nile infection. Of those, five had meningitis -- inflammation of the brain and spinal cord lining -- and eight had encephalitis, or swelling of the brain itself. Three had flaccid paralysis akin to that seen with polio.
All but one patient developed some form of movement trouble, such as tremors, jerkiness and symptoms resembling Parkinson's disease. That may be because the virus can attack areas of the brain involved in motion, including the thalamus, basal ganglia and the pons.
"These movement disorders can be seen when you damage those parts of the brain," Sejvar says. Flaccid paralysis occurs when the virus attacks cells in the spinal cord, called anterior horn cells, he explains.
Although one person in the study group with confirmed West Nile infection died of the disease, the outlook for patients with the disease was generally quite good. All five who developed meningitis, for example, were able to return to work within eight months and reported feeling normal or nearly so, the researchers say. Even patients with severe encephalitis rebounded well, with five of the eight mostly recovered within four months of falling ill.
Still, headaches, nerve pain and fatigue often lasted several months. Difficulty walking and other movement problems also lingered in six patients, including in all three people with flaccid paralysis.
"There really is no improvement in the weakness," Sejvar says. "Many of these patients will experience permanent paralysis."
More information
For the latest on West Nile, check with the U.S. Centers for Disease Control and Prevention or the National Institutes of Health.
