Virus’ lingering sting
When West Nile disease invaded the New World four years ago, scientists knew they were dealing with a rare and potentially deadly pathogen. What they did not immediately grasp, however, were the various ways it could trigger debility.
Now, as the virus spreads westward, medical researchers are producing evidence revealing how West Nile disease can, on occasion, seem uncannily like a scourge from the past.
Just as people stricken with polio generations ago developed a muscle weakness or paralysis after infection, so it is now for some infected with West Nile. Recognizing that such paralytic conditions can be a consequence of infection, federal health officials earlier this year expanded their definition of what it means to be infected with the virus.
Basically, fever and flu-like symptoms constitute mild versions of the disease. Meningitis and encephalitis typify the more serious and life-threatening forms. But federal health officials acknowledge that patients with muscle weakness reminiscent of polio, or even a stroke, may be infected with the seasonal virus.
“West Nile is not polio. The two are caused by very, very different viruses,” said Dr. Dobrivoje Stokic, director of neurological recovery at Mississippi Methodist Rehabilitation Center in Jackson. He and a colleague, Dr. Arturo Leis, were the first in the nation last year to describe the similarity between the two infections. Their key discovery: West Nile virus and poliovirus are capable of homing in on the same cells in the central nervous system and inflicting damage.
Those cells, known interchangeably as anterior horn cells and muscle neurons, are housed in the spinal cord’s gray matter and control muscle movement. Because the discovery is still so new, and the disease is in only its fifth season in the United States, scientists still don’t know whether the loss of muscle function in patients is permanent.
“Right now we don’t know if the long-term prognosis is similar to polio or if it is different,” Stokic told Newsday recently. “In the long run, we really don’t know about the recovery of patients with West Nile virus.”
Shortly after Stokic and Leis announced their discovery, Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, voiced surprise. He told a U.S. Senate committee that medical textbooks contain no mention of damage to anterior horn cells in relation to West Nile. And there is now concern, Fauci said, that the range of disease manifestations is even greater than originally thought.
Persistent headaches and muscle aches, memory loss, stiffness and involuntary muscle contractions also may be linked to West Nile.
Like polio, West Nile is a summertime affliction. But the mosquito-borne infection affects far fewer people than did polio in its day. West Nile primarily afflicts adults and sometimes proves fatal in the elderly. Polio was a childhood disease.
Even though a majority of children exposed to the virus never developed symptoms, the disorder took a dramatic toll. At the height of the polio epidemic in the early 1950s, an estimated 60,000 cases occurred annually in the United States and about 3,000 children died each year of the infection. Because the disease affects the central nervous system, it also could cause meningitis.
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Seasonal infections
By comparison, 2,267 West Nile cases had been reported nationwide this year as of Sept. 4, and 43 people have died. Infections tend to peak in late summer. Most people infected with West Nile never know it. Only one in 150 who contract the virus goes on to develop meningitis or encephalitis. Studies have shown that muscle weakness and paralysis can accompany meningitis, or the loss of muscular function can be the only symptom. So far, the doctors say, only a fraction of West Nile patients have developed polio-like muscle weakness or paralysis.
But it’s possible that some people, Stokic said, may have developed the problem and never connected it to West Nile.
Mark Lingley is convinced that muscle weakness in his left leg is a lingering effect of West Nile. His doctors have not confirmed the connection; his neurologist wants to conduct tests to evaluate the weakness.
A celebrated designer of custom shirts, mostly for Wall Street executives, Lingley knows too well what a West Nile infection can do.
“My left leg is constantly numb and has this drag effect. It comes down slower when I walk,” said Lingley, who was diagnosed with West Nile meningitis two years ago. The muscle weakness has been a persistent reminder. “I have no control over this.”
His mission has been to sound a warning about the danger of mosquitoes -- and to have signs posted near sites where they are known to swarm.
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A follow-up study
Scientists, meanwhile, are trying to sort out findings in patients studied to date. The initial study conducted by Stokic and Leis examined the conditions of six patients treated at their Mississippi rehabilitation center. The researchers have since received a grant from the National Institutes of Health to conduct a follow-up investigation.
“What we’ve seen basically,” said Stokic of the polio-like symptoms, “is a muscle weakness appearing in, say, one arm on one side of the body and in the leg on the opposite side.” Or, the weakness may occur in different regions of the same leg.
Such asymmetry is a hallmark of polio, he said.
West Nile virus and the pathogen that causes polio are members of unrelated viral families. West Nile disease is caused by a wily microbe known as a flavivirus. Members of this class, which include the dengue, malaria, yellow fever and St. Louis encephalitis viruses, are generally borne by mosquitoes.
Poliovirus belongs to the group of submicroscopic germs called picornaviridae. In a study of patients reported recently in the Journal of the American Medical Assn., researchers from the Centers for Disease Control and Prevention found a distinct pattern in the onset of muscle weakness or paralysis in people infected with West Nile disease -- one they said looked identical to the pattern associated with polio.
“We’ve noticed that symptoms develop very quickly,” said Dr. James Sejvar, who led the study for the CDC. Stokic also discovered a rapid onset of weakness.
Lingley hopes doctors work quickly to develop a better understanding of West Nile and its many manifestations. “People really don’t know what this disease is like unless they live through it.”
