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http://www.nytimes.com/2002/08/20/health/20NILE.html

Deaths From West Nile Virus May Be Tied to a Gene Variation

By THE ASSOCIATED PRESS

ASHINGTON, Aug. 19 (AP) — Only about one in five people infected with the West Nile virus develops a life-threatening illness, and a new study in mice suggests that a gene variation may be the reason some become very sick from the mosquito-borne virus while others recover easily.

Experts say the research is an important step toward finding a drug to treat West Nile, a virus that has caused 11 deaths in the United States this year.

The Centers for Disease Control and Prevention said today that 251 people in 12 states have been infected so far this year.

For most people, West Nile causes only flulike symptoms. But for some patients, particularly the young and the elderly, West Nile can be a killer, causing a swelling of the brain that can be lethal.

Scientists at the Pasteur Institute in France searched for a gene variation that might explain the difference in susceptibility.

The French first tested a series of laboratory mouse strains to find a genetic type that was most likely to die after being exposed to the West Nile virus.

They found that animals in the mouse strain called BALB/c all died within 13 days when injected with the West Nile virus. When these animals were mated with other mouse strains, some of the offspring died from the virus, while others were little affected.

By analyzing the genes of both the BALB/c mice and the mixed strains with a high rate of West Nile deaths, the researchers isolated a specific gene variation that increased the susceptibility to the virus, the researchers report. They called the variation the West Nile gene.

Dr. Jean-Louis Guenet of Pasteur, a co-author of the study appearing this week in The Proceedings of the National Academy of Sciences, said the West Nile gene allows the virus to cause disease by blocking production of a group of proteins that normally prevent viruses from reproducing inside a cell.

The exact gene variation has not been found yet in humans, Dr. Guenet said. But other researchers said the study was still important.

"The possibility of developing a drug is why we are excited about this finding," said James M. Meegan, a virology research program leader at the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

Dr. Meegan said that his agency was financing research on three vaccines for West Nile virus and that one might be ready for human trials next year.

Today, health officials in Texas said they were performing more tests to confirm whether a 52-year-old woman died from West Nile virus. It would be the first such death in the state this year.

The unidentified woman was hospitalized on Aug. 8 and died on Friday, said Kathy Barton, a spokeswoman for the Houston Department of Health and Human Services.

The Centers for Disease Control and Prevention "is testing it," Ms. Barton said. "We feel like it is going to be confirmed."

But she added that it would be at least two weeks before testing was concluded.

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