HOUSTON -- An elderly northwest Harris County woman, who was described by officials as fairly healthy and active, is the county's first confirmed West Nile virus death this year.
The woman, whom health officials did not identify, was admitted to an undisclosed hospital for several days in late August with symptoms her doctors first thought was stroke. The woman, in her late 70s, had slight paralysis.
"She deteriorated," said Cindy Kilborn, Harris County's chief epidemiologist. "It can rapidly progress with someone who has a challenged immune system." Typically, mid-July through September is the most likely time for humans to contract this mosquito-borne virus.
However, Ray Parsons, the director of the county's mosquito control division, said officials are still finding mosquitoes and dead birds with the virus. For example, a recent batch of 29 dead birds tested positive for West Nile.
West Nile virus circulates between mosquitoes -- primarily culex -- and birds. Mosquitoes that bite the birds can become infected and transmit the virus to other birds, animals and humans.
"West Nile season is not over. People still should be taking precautions," Parsons said. "We still have the potential into October, and we do have records of St. Louis encephalitis (another mosquito-borne disease) into November." Human cases of West Nile virus infections in the county have been declining since it first invaded the area in 2002.
That year, the county reported 99 confirmed human cases and six deaths from the virus. In 2003, there were 62 human cases in the county and three deaths. So far this year, there have been 23 confirmed human cases and one death. Statewide, there have been eight West Nile deaths this year.
County officials credit a number of factors for the decline in human cases, including the county's aggressive mosquito control measures and the higher percentage of people who have built an immunity to the virus.
Parsons said the virus has been particularly prominent in the northwest portion of the county.
"We had already been spraying in the northwest area before the death and after the death," he said. "There's no place in the county free of the culex mosquito." West Nile symptoms occur five to 15 days after being bitten. Most people with West Nile virus show no symptoms or mild symptoms such as low-grade fever and headache. Severe symptoms include high fever, stiff neck, muscle weakness, disorientation and coma.
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c.2004 Houston Chronicle