Dallas County officials said they see no need for now for more aerial spraying to combat West Nile virus after receiving encouraging data Thursday about the first round of aerial spraying.
The U.S. Centers for Disease Control and Prevention reports a 93 percent reduction in disease carrying mosquitoes in areas of the county that received two nights of aerial spraying earlier this month.
"The city of Dallas did the right thing," Mayor Mike Rawlings said. "Mosquitoes were killed, no one was hurt by the spraying and, if we hadn't executed this plan, we now have information that the growth in mosquito population would not have gone down on their own, but probably would have risen," he said.
The preliminary report will be followed by much more detailed research. Dr. Janet McAllister, of the CDC, said trapping and testing mosquitoes must continue in Dallas County this summer, with more ground spraying likely.
"The decision to continue aerial spraying or what ground spraying goes on needs to be driven by ongoing surveillance of what the mosquito population is doing," she said. "The decision again, is up to the local jurisdiction, but it needs to be driven by the surveillance."
The mosquito season will continue until there is a freeze and officials urge residents to keep their guard up by wearing long sleeves and pants, using insect repellent and removing standing water where mosquitoes may breed.
Dallas County Judge Clay Jenkins said the county still expects more human cases because of a lag time in reporting the cases and because mosquito control plans will not kill all mosquitoes.
"West Nile is here to stay," he said.
The number of human cases reported this year in Dallas County rose to 322 on Wednesday; 13 of them were fatal.
"We're going to look at this," Jenkins said. "We're going to see whatever we can improve in our protection."
He and Rawlings attended a late afternoon press conference with McAllister to release the new CDC data.
Rawlings said the city would continue to push prevention methods and that this year has changed the way local officials monitor and control the mosquito population.
"While we're not perfect, everyone here at the podium is doing everything we can to minimize illness and minimize death," he said.
NBC 5's Greg Janda contributed to this report.