Zika Resource Center
Zika Resource Center
August 01, 2016
3 min read

CDC warns pregnant women to avoid area in Miami over Zika fears

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In what is thought to be an unprecedented warning, the CDC is advising pregnant women to stay out of an area of Miami where health officials believe local transmission of Zika virus is occurring.

Florida Gov. Rick Scott announced today that the number of cases of locally transmitted Zika had climbed from four to 14 over the weekend after 10 more people were identified, including six asymptomatic patients who were identified via a door-to-door survey.

The Florida Department of Health (DOH) still believes the virus is being transmitted by Aedes aegypti mosquitoes only in a small area north of downtown Miami encompassing the neighborhood of Wynwood in Miami-Dade County.

It was believed to be the first time the CDC has asked people to avoid part of the continental United States because of a health concern, CDC Director Thomas R. Frieden, MD, MPH, said.

Thomas Frieden, MD

Thomas R. Frieden

“We can find no similar recommendation in recent years,” Frieden said during a teleconference with reporters.

Mosquito control not working

In the past, the CDC has issued travel warning for countries where Zika is being spread locally by mosquitoes, including the U.S. territory of Puerto Rico, which has been hit hard by the virus. But Frieden said last Friday that the CDC would not issue a warning for the area in Miami where the first-ever cases of local transmission in the continental U.S. were reported unless they continued to occur.

Today, he said mosquito control measures were not as effective as hoped, either because the mosquitoes have developed a resistance to the types of sprays being used, or because they are breeding in so-called “cryptic” sites that are difficult to find.

Additionally, A. aegypti mosquitoes are difficult to track and kill in areas like the “mixed-use” location in Miami where these cases are occurring, which features industrial, commercial and residential buildings, because control measures must be tailored, Frieden said.

For these reasons, the CDC decided to issue advisories for the approximately 1 square mile area, including several for partners of women who are pregnant or are planning to become pregnant.

All of the agency’s recommendations apply to people who have traveled to or are living in the affected area as of June 15, the earliest known date that one of the patients could have been infected, Frieden said.

Although Zika is primarily contracted through the bite of an infected mosquito, the virus also can be sexually transmitted by men and women, and infection during pregnancy can cause microcephaly and other serious birth defects, even among women who are asymptomatic.

“As we’ve said since the beginning of this unprecedented outbreak, we are learning something new about Zika every day,” Frieden said. “We make decisions on updating our recommendations and guidance on a day-to-day basis.”

Florida seeks help from CDC

At Scott’s request, the CDC is sending an eight-person emergency response team to help respond to the outbreak.

Mosquitoes do not travel far in their lifetimes — only about 150 meters — and Frieden said 12 of the 14 patients in Florida were likely infected in an area approximately this size located near the center of the 1 square mile space that is the subject of the CDC’s advisories.

Frieden said they will “undoubtedly” discover more infections in the area, but that widespread transmission still was considered unlikely.

“New assessments of mosquito populations and new test results have found persistent mosquito populations and infections in the area,” Frieden said. “This shows that there is a risk of continued transmission.”

Thus far, testing has not turned up any mosquitoes carrying the virus, and Frieden said that was unlikely to change. The DOH has organized increased spraying and mosquito abatement measures in the area. Meanwhile, Zika prevention kits and repellent are being distributed at local obstetrician-gynecology offices and DOH locations in Miami-Dade and Broward counties, the department said.

Before Friday, each of the more than 1,600 cases of Zika virus that had been reported in the continental U.S. were acquired outside of the country. – by Gerard Gallagher


CDC. Advice for people living in or traveling to Wynwood, a neighborhood of Florida. 2016. http://www.cdc.gov/zika/intheus/florida-update.html. Accessed Aug. 1, 2016.

Disclosures: Frieden is the director of the CDC. Scott is the governor of Florida.