(DALLAS) -- For the first time in decades, Dallas has launched an aerial attack against the West Nile virus, sending two small planes to douse the city with mosquito-killing pesticides.
The planes sprayed pesticides across 49,000 acres of Dallas County Thursday night in North Texas' latest war on the mosquito population. Officials are in a race against the clock, fighting the worst nationwide outbreak of the West Nile virus, which has already killed 10 people in Dallas and sickened more than 200.
The Centers for Disease Control and Prevention has reported 693 cases and at least 26 deaths nationwide in 43 states, with Texas being the epicenter. It's the first time in more than 40 years that Dallas County has used an aerial insecticide program. Mayor Mike Rawlings had hoped it did not have to come to this.
"It's a difficult issue because there's a lot of sentiment people don't want this, and there's a fear of the unknown, but in some ways, it's very simple," Rawlings said. "When you are dealing with someone's life, that should come first and foremost."
The decision to spray pesticides from above was unpopular with many residents who worry about the potential effect on people, animals and the environment. Crews have been spraying on the ground for weeks, but the death toll kept rising.
Dallas County Judge Clay Jenkins said an aerial assault on the mosquito population was the right call.
"But this is not a decision that I could base on public opinion," he said. "This is a decision that we had to make on science."
The EPA says the chemical mist is only harmful to people or pets if it's swallowed, but some doctors disagree, saying people with asthma or respiratory problems are at risk.
"I tell them [patients], if they can and they're really sensitive, to leave town," Dr. Alfred Johnson of Dallas said.
The pesticide is toxic to bees and fish, which is why some homeowners scrambled to cover their backyards, gardens and ponds.
Dr. Richard Besser told ABC's Good Morning America Thursday that last year's mild winter is the reason for the drastic outbreak.
"You count on that cold to kill mosquitoes and that didn't happen," he said. "So, mosquitoes this year are really abundant."
Besser estimates that at least 12,000 people have already been sickened by the West Nile virus in 2012. People who are 50 and older have been hardest hit by the virus after they're infected, Besser said.
Eighty percent of the people who contract the West Nile virus have no symptoms and their body eventually gets rid of it, according to the CDC. The remaining 20 percent experience flu-like symptoms.
One in 150 people will develop more severe forms of the disease and experience neurological symptoms and brain swelling, Besser said.
Copyright 2012 ABC News Radio