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Mosquito-Borne Brain Infection More Severe Than Thought

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The children ranged in age from 6 months to 15 years. None died, although several survived only because of aggressive intensive care.

Nearly as frightening is the finding from follow-up studies of 28 children who had the most severe symptoms. Many of these children had long-lasting changes in their behavior and ability to do their schoolwork. A normal IQ score is 100, but more than a third of these children had a full-scale IQ score of 79 or less.

"We found in following children over the long term that in about a third of children old enough to be tested, those children did seem to have suggestion of developmental problems, such as increase in hyperactivity measures in more than half of the kids," McJunkin says. "There was also a suggestion of a decrease in average IQ compared to the norm."

These changes aren't always obvious at first.

"The problems were not there immediately," Johnson says. "One year went by and then one day Ronnie was playing in the living room with his brother and fell on the couch. I thought he was joking, but then I saw he was out of it. The doctors realized he would start having more seizures at that point.

"I've cried about it -- Ronnie seemed totally different from the son I had before," she continues. "His whole attitude had changed. He seemed more defiant; he had learning impairments that we are still working on. He always had done really well in school, and it seemed after the encephalitis, he had no drive. It seemed he was always tired and always moody, not wanting to cooperate. But he's starting to improve now."

John R. Schreiber, MD, MPH, is chief of pediatric infectious diseases at Case Western Reserve University's children's hospital in Cleveland. He praises the McJunkin team for providing sorely needed information. He notes that while La Crosse encephalitis is a serious disease, other mosquito-borne encephalitic diseases firmly established in the U.S. can be far worse.

"The [aftereffects] of La Crosse encephalitis are worse than we thought but not devastating," Schreiber tells WebMD. "In the scheme of things, these are mild deficits. For example, eastern equine encephalitis virus can destroy your brain -- now that is very disturbing. In the fear ratio, La Crosse is considered relatively mild.

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