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West Nile Outbreak on Track to Be Worst Ever

47 Deaths; Texas Especially Hard Hit

West Nile Symptoms continued...

And these patients are lucky compared to those who get what the CDC calls "neuroinvasive disease." In about one in 150 people, West Nile virus infects the brain (encephalitis) or the spinal cord and connecting nerves (meningitis). So far this year, there have been 629 reported cases, with 58 cases of paralysis.

"The meningitis or encephalitis can cause paralysis that affects one or more limbs. It can also affect breathing. It is one of the more severe and dreaded complications," Petersen said. "With meningitis, symptoms include headache, stiff neck, eye pain, and fever. Encephalitis, infection of the brain itself, causes cognitive problems, where people can't think properly. It can also cause coma, along with all the symptoms of meningitis as well."

And there's another risk. Last month, Baylor University researchers reported that West Nile virus doesn't go away in some people. The virus hides in the kidneys. Over the course of years, it causes kidney disease that worsens over time.

People with neuroinvasive West Nile disease were most likely to have long-lasting infection and kidney damage. But this also happened to about 9% of those with mild or no symptoms.

Other laboratories have yet to confirm these findings. "But if they are true, they are of importance," Petersen said.

West Nile Virus: Who's at Risk?

Most serious cases of West Nile virus occur in people over age 50. This year, 61% of cases have been over 50, and 39% have been over 60. The elderly are at particularly high risk.

Infants are not at high risk, as very few infant infections have been reported. So far this year, there's been only one reported West Nile infection of an infant.

There have been isolated reports of pregnant women passing the infection to their unborn children, but so far most women known to be infected with West Nile virus have given birth to healthy, uninfected babies.

It's not yet clear whether people with weakened immune systems are at higher risk.

Because West Nile virus is spread by mosquitoes, the CDC notes that people who spend a lot of time outdoors -- especially during dawn and dusk -- are at higher risk.

West Nile virus can be transmitted by blood transfusion. In the U.S., blood is tested for West Nile virus. So far this year, West Nile virus has been detected in 242 samples of donated blood. There have been no known infections via transfusion, and the U.S. blood supply is considered safe.


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