There are growing West Nile Virus concerns in Williamson County.
The County Health District says it's investigating the first likely human case in the county. The patient is a 55-year-old man.
They've decided to spray after finding nine samples of mosquitoes carrying the virus. Two were in Cedar Park, three in Bartlett, two in Georgetown, one in Hutto and one in the southwest part of the county. The chemicals that are typically used are permethrin and resmethrin.
"They're the safest insecticides known in the United States," Williamson County and Cities Health District Executive Director John Teel. "They're also commonly found in our household products. If you go find wasp and hornet spray you're going to find the same chemicals in those."
The trucks will be spraying through the weekend and early next week, but not on Halloween.
Health officials say the best way you can protect yourself is spraying insect repellent and dumping standing pools of water which serve as breeding grounds for mosquitoes.