VOA标准英语2012--Texas Health Officials Study West Nile Outbreak
时间：2012-08-24 03:36:08
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Texas Health Officials Study West Nile Outbreak
Technicians in the state's mosquito laboratory are examining mosquito corpses1 sent from all over Texas, at the Texas Department of Health Services Laboratories in the capital of Austin.
State Laboratories Director Grace Kubin said technicians use animal tissue that is susceptible2 to West Nile virus to test the mosquito samples.
“We add in, essentially3, the ground-up mosquitoes," said Kubin. "We have to grind them up; that releases the virus. And now we have that in a liquid form and we can use that to infect the cells.”
Kubin said the tests provide results within 48 hours so the lab can advise local officials on what action to take.
Mosquitoes aren't born with West Nile virus. They generally get it from biting birds that are infected.
Right bird, right time
To ingest the virus, mosquitoes need to find, so to speak, the right bird at the right time, according to Texas State Veterinarian Tom Sidwa. Some birds survive the virus.
“The birds only have the virus remaining in their blood from one to four days after they get infected. Then they have life-time immunity4, so you have to find that bird that has the virus in its blood stream," said Sidwa.
From the Austin command center, Sidwa manages the state effort to track the West Nile outbreak. He said his team got an early warning months ago from routine testing of donated blood.
“This year we got advance notice that there was activity by virtue5 of that testing and people who were donating blood testing positive for West Nile. That does not mean they are sick. Some of them may be, but they have the virus in their system,” he said.
Most infected people unaware6 of it
Sidwa said most infected people are unaware of it. Symptoms can include fever, headache and feeling tired. For the small percentage whose brains are affected7 by the virus, it can be debilitating8 and even deadly.
“The way it manifests is everything from 80 percent of the people with no symptoms, to 20 percent with a lesser9 disease, and roughly one percent - or one in 150 - will develop the severe neurological form of the disease,” said Sidwa.
As the hot weather subsides10 in the weeks ahead, Sidwa said he expects the number of reported West Nile cases to taper11 off. And he said what has been learned this year will help in dealing12 with future outbreaks.
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