HOUSTON (CN) - Mosquitoes have not yet tested positive for the Zika virus in the United States, and Texas officials say vigilant citizens can help stamp out the threat.
Ten Texans have tested positive for the virus. Nine were infected while traveling abroad. A Dallas County resident got it from sexual contact with someone who was infected in Venezuela, according to the Texas Department of Health Services.
Seven of the state's Zika cases are in Harris County, the state's most populous.
Chris Van Deusen, a spokesman for the Department of Health Services, said he could not discuss the health of the 10 infected people.
"But the virus only lasts in the blood for about a week, so typically, individuals would have recovered by now," he said.
Dr. Mustapha Debboun, director of the Harris County mosquito eradication department, said his staff checks traps in 268 areas around the 1,778-square-mile county and takes mosquitoes from them for lab testing.
"The mosquitoes that we're catching, which is small numbers, they don't have any viruses in them right now. Whether it's dengue virus, chikungunya, or St. Louis encephalitis virus, or West Nile Virus, no viruses in mosquitoes at this moment," Debboun said in an interview. "At this moment."
He said Harris County typically does not start spraying for mosquitoes until May.
In summer months, the thick jets of mist that county trucks emit on Houston streets contain a mixture of malathion and permethrin.
"A truck goes by with a machine on the back and the machine has a tank with pesticide in it, and it's called ultra-low volume and displaces particles in the air because supposedly mosquitoes will be flying and the pesticide dispersal hits them," Debboun told Courthouse News.
He said the county's spraying regimen is not dictated by month or location, but when mosquitoes "become hot with viruses."
The mosquitoes that spread the Zika virus are from the Aedes genus and prefer to breed in open water containers near people's homes. Since the mosquitoes seldom travel more than 300 meters from where they are born, drying up the homestead can be key to preventing infection.
"People really need to get involved by helping us, in removing the containers that they have in their front yards and back yards, whether it's a tire, bucket or pail, because that's where the mosquitoes are breeding," Debboun said. "So they are creating the problem for themselves, and if they want to help be part of the solution, they really have to remove those containers.
"If they do that we won't even have to spray, because they will deny the mosquito a place to breed."
Tom Frieden, director of the Centers for Disease Control and Prevention, testified at a congressional hearing Wednesday that Aedes mosquitoes are active during the day, hide indoors under tables and in other hard-to-reach places, and can bite a large number of people quickly.
Debboun, a retired Army colonel, said the Aedes mosquito does not breed in bayous, marshes or swamps, so his department does not spray in those areas.
"Yes, there are other mosquitoes that breed in swamps and all that, but they're not disease-carriers; they are just nuisance mosquitoes."
Van Deusen, with the state health department, said Texas will help counties by contracting with insecticide sprayers in case of an emergency, such as the West Nile Virus outbreak that struck Dallas County in 2012.
At least 10 deaths in Dallas County that year were attributed to the virus, which causes an infection that inflames the brain.
Though researches have yet to confirm the suspected link between Zika virus and the birth defect microcephaly, Frieden told Congress that the CDC found the most convincing evidence yet in a recent study that found Zika's genetic material in the brain tissue of two infants who died of microcephaly.