MIAMI — South Beach has been identified as a second site of Zika transmission by mosquitoes on the U.S. mainland, and containing it there will be difficult because high-rise buildings and strong winds make it impractical to spray the from the air, officials said Friday.
Five cases of Zika have been connected to mosquitoes in Miami Beach, bringing the state's caseload to 36 infections not related to travel outside the U.S., Florida's governor and health department announced Friday.
The discovery prompted the U.S. Centers for Disease Control and Prevention to announce that it was expanding its travel warning for pregnant women to include an area in Miami Beach known for nightclubs, pedestrian thoroughfares and beaches.
The CDC previously warned pregnant women to avoid the Wynwood arts district in Miami. In its statement Friday, the agency said pregnant women may also want to consider postponing nonessential travel throughout Miami-Dade County if they're concerned about potential exposure to the mosquito-borne virus.
"We're in the midst of mosquito season and expect more Zika infections in the days and months to come," said CDC director Dr. Tom Frieden. "It is difficult to predict how long active transmission will continue."
Aerial spraying and door-to-door operations on the ground have cut mosquito populations in Wynwood by up to 90 , but Zika may be continuing as mosquitoes breed, Frieden told reporters Friday.
"The mosquitoes are persistent and we won't know for a couple of weeks whether these aggressive measures have worked," Frieden said.
Aerial spraying isn't practical over South Beach because of the height of its buildings and strong winds over the narrow island city, Frieden said. Officials will be limited to spraying for mosquitoes at ground level in the highly populated area.
"Miami Beach does have a series of characteristics that make it particularly challenging," Frieden said.
Two of the people infected in Miami Beach are Miami-Dade County residents, and three are tourists, including one man and two women, Scott said. The tourists are residents of New York, Texas and Taiwan.
The new area of infection in South Beach is roughly 1.5 square miles between 8th and 28th streets, according to Florida's Department of Health.
Three vacuum trucks purchased to help Miami Beach fight rising sea levels have been used since the beginning of the year to drain water in low-lying areas where mosquitoes could breed, said Roy Coley, the city's infrastructure director.
The city also has been sending workers to fill potholes collecting water in alleys and fix leaky beach showers, in addition to applying pesticides to the area's many construction sites and flood-prone residential streets, Coley said.
"Our call volume has increased significantly," Coley said.
Possible infections outside Wynwood and Miami Beach also are being investigated.
Zika infection can cause severe brain-related birth defects, including a dangerously small head, if women are infected during pregnancy. But the virus only causes mild, flu-like symptoms in most people, making it difficult to confirm local transmissions, the CDC said.
"For this reason, it is possible that other in Miami-Dade County have active Zika transmission that is not yet apparent," the CDC's statement said.
This story has been corrected to reflect that the Health Department spokeswoman, not the governor, said officials believe mosquitoes transmitted the Zika.