West Nile Virus Can Cause Polio-like Symptoms

Researchers conducted tests on the bodies of four people who died after developing polio-like symptoms along with West Nile virus infections. The research, which is being presented during the American Academy of Neurology Annual Meeting in Honolulu, March 29-April 5, 2003, provided further evidence that West Nile virus can cause the polio-like symptoms of muscle weakness, acute paralysis and impaired breathing.

"As we head into another season with this virus, it's very important for doctors to recognize that people with symptoms of sudden muscle weakness or paralysis could have West Nile virus," said the study's lead author, Jonathan Fratkin, MD, of the University of Mississippi Medical Center in Jackson.

In some cases, these symptoms have been misdiagnosed and patients have been given treatments that could have been harmful or even life-threatening.

"These were difficult cases, because West Nile virus had not previously caused these types of symptoms, and the symptoms were similar to that of another neurological disorder, Guillain-Barré syndrome," Fratkin said.

Fratkin and his colleagues have seen eight cases of polio-like paralysis due to West Nile virus, and several other cases have been reported around the country. This research reports on four of the Mississippi patients who died within weeks or months after developing the virus.

The autopsies found signs of viral infection -- inflammation of the gray matter of the spinal cord and inflammatory cells clustered around dying cells in the spinal cord known as anterior horn cells, the same motor neurons that cause some of the disabling effects of polio. The autopsies also ruled out other causes of the symptoms, such as a lack of blood flow or oxygen to the brain. However, the tests to see whether the West Nile virus was present at the time of death were negative.

"Enough time had elapsed between when these people became sick and when they died, and they had been showing improvement before they died, so it's possible that the virus was gone from their bodies," Fratkin said. "Another possibility is that our tests are not sensitive enough to detect the virus."

Fratkin noted that West Nile virus can survive in some blood products. "Doctors should consider West Nile virus as a cause of sudden muscle weakness or paralysis that occurs in people who have recently had a blood transfusion or an organ transplant," he said.

The researchers stressed that most people who become infected with West Nile virus do not get sick, or they experience relatively mild, flu-like symptoms. According to the Centers for Disease Control and Prevention, less than one percent of those infected with West Nile virus will develop a severe illness.

The Mississippi group's research was supported by Wilson Research Foundation of Jackson, MS, which is affiliated with Methodist Rehabilitation Center.

The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research.