United States health officials say pregnant women should not travel to an area north of downtown Miami that has active Zika transmission. The agency said on Monday that it is also recommending that pregnant couples in the area avoid mosquito bites with clothing and repellant.

On Monday, the director of the U.S. Centers of Disease Control and Prevention (CDC), Dr. Tom Frieden, announced that over the weekend more infections of Zika were identified in a small area in Miami-Dade County, just north of downtown. It is determined that the area has active transmission of the virus, which is why the CDC is advising pregnant women to not travel to that region. In total, 14 people are infected with the virus from local mosquitoes. (You can see a map of the affected region here).

The CDC also is sending an emergency response team to the area, after Florida governor Rick Scott called on the CDC to do so. Some members of the team are already on the ground and others are on the way. The CDC says it will re-assess the situation every day.

Despite the daily use of spraying to control the local mosquitoes, Florida vector control specialists are still seeing a lot of mosquito larvae and high numbers of the aedes aegypti mosquito, which spreads Zika. It’s not yet clear why the numbers remain high.

Dr. Frieden said the CDC believes this is the first time a federal group has advised Americans not to travel somewhere in the continental United States due to a health risk. “We wish we had all the answers, but the fact is this is a new phenomenon,” said Frieden. “We continue to learn each day about Zika.”

Despite the fact that Zika puts pregnant women at risk for having babies with the severe birth defect microcephaly, Frieden acknowledged to reporters that they continue to run into apathy over the virus and that it can be difficult to get the public to want to change behavior.

 

This article originally appeared on Time.com.