TERRA CEIA ISLAND, Fla. • The Florida Department of Health has issued a statewide mosquito-borne illness advisory Wednesday after four locally contracted cases of malaria were reported along the Gulf Coast south of Tampa.

On Monday, a health alert issued by the Centers for Disease Control and Prevention also noted that another case has been detected in Texas, marking the first time there has been a local spread of malaria in the United States in 20 years.

The four residents in Sarasota County received treatment and have recovered, according to the state’s Department of Health advisory. Malaria, caused by a parasite that spreads through bites from Anopheles mosquitoes, causes fever, chills, sweats, nausea and vomiting, and headaches. It is not spread person to person.

It’s the threat of the mosquito-borne illness that concerns Kathleen Gibson-Dee, who lives on Terra Ceia Island, which is about 20 miles north of Sarasota County.

Even though no malaria cases have been reported in Manatee County, where Terra Ceia is located, Gibson-Dee said that she’s now routinely using bug repellent while working in her garden.

“I don’t go out without it,” she told The Associated Press on Tuesday. “And we don’t go out in the evening because you can see clouds and clouds of bugs now. They may not all be mosquitoes, but there’s certainly mosquitos out there.”

Another resident, Tom Lyons, says news of the malaria cases “makes me take mosquito protection a little more seriously.”

The mosquito population thrives in Terra Ceia because “it’s an island surrounded by a lot of shallow water and mangroves, and ideal places for mosquitoes,” Lyons said.

Officials in Manatee County have ramped up efforts to control the mosquito population.

Chris Lesser, director of the Manatee County mosquito control district, said they’re primarily using helicopters to combat the mosquito population because they cover between 15,000 and 20,000 acres in one night. A truck can only cover around 1,000 acres a night, he said.

“We really want to focus on killing the adult mosquito before they have the opportunity to feed on one person that may be infected with malaria and then transmit that disease to a second person,” Lesser said.