South Beach has been identified as a second site of Zika transmission by mosquitoes on the U.S. mainland, Florida officials said 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 the tourist-friendly area of Miami Beach.

Ocean Drive, in Miami’s South Beach, which has been cited for Zika transmission. iStockphoto

In a statement issued shortly after Gov. Rick Scott and health officials released the latest information, the CDC 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.”

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Five cases of Zika have been connected to Miami Beach, bringing the state’s caseload to 36 infections not related to travel outside the U.S., Gov. Rick Scott said at a news conference. In response to a follow-up question from The Associated Press, Florida Department of Health spokeswoman Mara Gambineri said officials believe the cases were transmitted by mosquitoes.

Two of the infected people 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.

Scott described the new area of infection in the narrow island city as just under 1.5 miles between 8th and 28th streets.

Another infection zone was previously identified across a roughly 1-square-mile area encompassing Miami’s Wynwood arts district.

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 (or no symptoms at all) in most people, making it difficult to confirm local transmissions, the CDC said.

“For this reason, it is possible that other neighborhoods in Miami-Dade County have active Zika transmission that is not yet apparent,” the CDC’s statement said.

In a press briefing, Frieden said that there are “undoubtedly more cases that we aren’t aware of.”

In addition to the travel warning for pregnant women to avoid the areas of Zika transmission, the CDC says pregnant women who live in or frequently visit these areas should take all precautions to prevent mosquito bites​. These include: