Pregnant women have been advised to avoid the Texas town of Brownsville due to concerns over the Zika virus. The Centers for Disease Control and Prevention on Wednesday warned that five home-grown cases had been recorded in the area recently, and the warm weather means the insects may still be active. “The CDC is designating the city of Brownsville as a Zika cautionary area [yellow area],” the center said in a statement. “With the new information that there has been local spread of Zika for at least several weeks, we conclude that pregnant women should avoid the Brownsville area—and make every effort to prevent mosquito bites if they live or work there,” CDC Director Tom Frieden said. The statement warned that people without any symptoms could spread the virus further, adding that it could take weeks for a Zika outbreak to become apparent due to the long incubation period. Brownsville’s spike in Zika infections comes after Florida officials declared last week that the active Zika zone in Miami was now clear.