By Andrea Lucia

DALLAS ( – Preliminary tests show aerial spraying in Dallas County may have dramatically decreased the number of mosquitoes carrying the West Nile virus.

The US Centers for Disease Control and Prevention released a report Thursday afternoon showing a 93 percent reduction in areas east and south of Dallas.

Those areas, including Rowlett, Mesquite, and Duncanville, were sprayed with pesticide from planes flying overhead on two consecutive nights earlier this month.

Those areas are the easiest to gauge and likely had the best result, according to Dr. Janet McCallister, of the CDC.

The new data also shows a “marked decrease” in mosquitoes in other parts of Dallas where aerial spraying was interrupted by storms.

Dr. McCallister, however, said, that data still needs to be further reviewed before it can be released.

Areas that received no aerial spraying, meanwhile, showed an increase in the number of mosquitoes, known to carry the virus, by an estimated 20 percent.

“The city of Dallas did the right thing. Mosquitoes were killed. No one was hurt by the spraying. And, if we hadn’t executed this plan, we now have information that says the growth in the mosquito population would not have gone down on their own, but probably would have risen,” said Mayor Rawlings.

Local leaders however warned there is still a risk of contracting the virus.

“Let me be clear, we will see more human cases,” said Dallas County Judge Clay Jenkins. “We cannot possibly kill every potential carrier mosquito. We will continue surveillance and we will take swift action when appropriate.”

Mayor Rawlings said, at this time, there is no need for further aerial spraying. The city’s ground spraying and public awareness campaign, though, will continue.

Dallas County Web Site

Map of Areas Sprayed (PDF) – Data released today is from Zone 3.  According to the CDC, data from zone 1 & 2 shows a decrease, but specific data is not ready for release.  Areas *not sprayed* show an increase.

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