Back to top

Pathological evidence confirms West Nile virus attacks the spinal cord and can cause acute flaccid paralysis similar to polio

Research findings published in prestigious international medical journal
Jim Albritton
Health and Research News Service

JACKSON, Miss.—The discovery by scientists at Methodist Rehabilitation Center that the gray matter of the spinal cord is the apparent target of the West Nile virus has been confirmed by pathological findings reported in one of the world’s most prestigious medical journals.

The international journal, The Lancet Infectious Diseases, has posted on its Web site research which identifies acute poliomyelitis as a cause for the muscle weakness and acute flaccid paralysis that is common in patients with West Nile infection. The journal published those findings in its print edition on Jan. 1, 2003.

Based on clinical findings first reported by the Center for Neuroscience and Neurological Recovery at Methodist Rehab in September, researchers led by Dr. Jonathan Fratkin in the Department of Pathology at the University of Mississippi Medical Center have confirmed that in people, just as in animals, anterior horn cells in the spinal cord seem to be a target of West Nile virus.

“The pathological findings confirm what we clinically observed in West Nile patients treated here at Methodist Rehabilitation Center,” said CNNR director Dr. Dobrivoje Stokic. “Our article in Lancet is significant because it is the first to include pathological evidence that indicates the West Nile virus attacks the spinal cord in humans and can cause acute flaccid paralysis similar to polio. More importantly, our research shows that paralysis may be seen in West Nile patients who do not have encephalitis or meningitis.”

Prior to the release of the CNNR's findings in September, national and local health guidelines emphasized that the West Nile virus was an attack on the brain and could cause encephalitis and meningitis. Although this was true, the CNNR research indicated that the virus could also attack the cells within the spinal cord that control muscle function, causing severe muscle weakness.

Earlier this year, due to the significance of the CNNR discovery, the New England Journal of Medicine and the Centers for Disease Control and Prevention expedited the release of articles reporting their clinical findings. The Journal of the American Medical Association also published the CNNR article that appeared in the CDC’s Morbidity and Mortality Weekly Report.

Now, with the release of the Lancet article, researchers are again urging public health officials to aware of their findings.

“It is important that physicians and public health officials in areas with active West Nile virus transmission realize that muscle weakness and acute flaccid paralysis could be a manifestation of West Nile poliomyelitis,” said Dr. Art Leis, CNNR senior scientist and project lead investigator. “If doctors see patients with symptoms that suggest involvement of the gray matter of the spinal cord—particularly in combination with fever, chills and headaches—with or without meningitis or encephalitis, then these patients should be tested for West Nile virus by sending serum to the Department of Health. Such awareness will help avoid the morbidity associated with unnecessary diagnostic procedures and inappropriate treatment.”

West Nile poliomyelitis should also be considered in recent organ transplantation or blood transfusion recipients who develop muscle weakness or acute flaccid paralysis said Dr. Leis.

“What we’ve discovered is significant and will enable physicians and public health workers nationwide to better characterize this illness,” said Dr. Stokic. “Our findings have greatly advanced the understanding of the spectrum of clinical presentations of West Nile virus infection.”

The first outbreak of West Nile virus in the United States occurred in 1999 when 62 people were hospitalized and seven died in New York. While reading the first autopsy reports, Dr. Leis noted that the brains were mostly unaffected and that all four patients were profoundly weak, suggesting that muscle weakness may be a significant risk factor in predicting morbidity and mortality.

“More than half of the confirmed West Nile cases have displayed severe muscle weakness,” Dr. Leis added. “Yet, this important symptom had previously received little scientific scrutiny.”

CNNR researchers suggest that physicians be aware of four symptoms of possible West Nile poliomyelitis:

  • Asymmetrical muscle weakness—where one arm or leg is weaker than the other
  • An absence or decrease in deep tendon reflexes
  • Acute change in bowel or bladder function
  • Respiratory muscle weakness especially where endotrachial intubation and mechanical ventilation is necessary

CNNR researchers hope that an increased awareness that the virus may target the spinal cord will result in better diagnoses and more appropriate treatments.

“A more accurate diagnosis and treatment will also lead to more accurate assessment of the effectiveness of prevention activities and mosquito control in humans,” added Dr. Leis.