As concerns over the Zika virus grow in Florida, the U.S. Centers for Disease Control and Prevention (CDC) issued an advisory Monday to pregnant women against traveling to Wynwood, a Miami neighborhood. State health officials have identified 10 additional Zika cases in Florida, bringing the total to 14, Florida Gov. Rick Scott said earlier in the day.

The CDC published a list of do’s and don’ts for pregnant women and their partners traveling to or living in Wynwood, which is within a one-mile section north of Miami. It said the precautions are for people who live in or traveled to the area after June 15.

“Pregnant women who live in or frequently travel to this area should be tested in the first and second trimester of pregnancy,” CDC said in the advisory.

The advisory also marked the first time the CDC has asked people to avoid an American neighborhood because of an infectious disease, CNN reported citing an agency spokesman.

According to CDC chief Tom Frieden, aggressive mosquito control measures in the state are not quite working to tackle the problem. This could be because mosquitoes are resistant to insecticides that are currently used or they may have been hiding in breeding areas. He also noted that Aedes aegypti, a mosquito known to carry Zika virus among other diseases, is difficult to control.

Meanwhile, Scott directed the CDC to launch an emergency response team to help the Florida Department of Health (DOH) in their investigation, sample collection and mosquito control efforts.

“DOH has been testing individuals in three locations in Miami-Dade and Broward Counties for possible local transmissions through mosquito bites. Based on DOH’s investigations, two locations have been ruled out for possible local transmissions of the Zika virus. DOH believes local transmissions are still only occurring in the same square mile area of Miami,” Scott said.

“For women who live or work in the impacted area and are either pregnant or thinking of becoming pregnant, I urge you to contact your OB/GYN [Obstetrics and Gynecology] for guidance and to receive a Zika prevention kit,” the governor added.

Last week, the U.S. Food and Drug Administration instructed blood centers in two Florida counties to halt collections until all units of blood are screened for the virus.

The Zika virus is mainly spread through the bite of an infected Aedes aegypti or Aedes albopictus mosquito and causes only a mild illness in most people. However, pregnant women are worst affected by the virus. Scientists have confirmed that infection during pregnancy can lead to the birth defect microcephaly, which results in unusually small heads in newborns.

According to Frieden, medical costs of each child born with microcephaly may require $10 over a lifetime.

“The tragedy of a preventable case of a severe birth defect is something I think we have to make very clear to people,” Frieden said, adding, “It is truly a scary situation but it is not immediately apparent to people that it is this kind of significant risk.”