U.S. health authorities urged pregnant women not travel to a Miami neighborhood on Monday as Florida officials identified 10 additional cases likely caused by local mosquito bites.
U.S. media said this could be the first time the U.S. Centers for Disease Control and Prevention (CDC) has advised the public not to travel a place in the continental United States.
The travel guidance recommended that pregnant women who have visited the one-square-mile (2.6-square-kilometer) area, just north of downtown Miami, should talk with their doctors and should be tested for Zika.
Pregnant women without symptoms of Zika who live in or frequently travel to this area should also be tested for Zika virus infection in the first and second trimesters of pregnancy, according to the U.S. CDC.
The U.S. agency also advised male and female sexual partners of pregnant women who live in or who have traveled to this area to use condoms or other barriers against infection during sex or abstain from sex for the duration of the pregnancy.
In addition, women and men who traveled to this area should wait at least eight weeks before trying for a pregnancy while men with symptoms of Zika wait at least six months before trying for a pregnancy.
"Pregnant women should avoid this area and make every effort to prevent mosquito bites if they live or work there," said CDC Director Tom Frieden.
"We apply the same criteria within and outside of the United States, and are working closely with the State of Florida and Miami health departments to provide preventive services, including mosquito control."
At Florida's request, the U.S. CDC is also sending an emergency response team with experts in Zika virus, pregnancy and birth defects, vector control, laboratory science, and risk communications to assist in the response.
Two CDC team members are already on the ground in Florida, three more will arrive today, and three more on Tuesday, it said.
On Friday, Florida Governor Rick Scott announced the first four locally spread cases of Zika in the continental United States.
Earlier on Monday, Scott said the total number of such cases, all in the same Miami area, has risen to 14.
Two of the 14 cases are women and 12 are men, and among the 10 new cases, six are asymptomatic and were identified from the door-to-door community survey that the Florida Department of Health is conducting, he said.
Scott said Florida would try to continue to keep residents and visitors safe utilizing constant surveillance and aggressive strategies, such as increased mosquito spraying, that have allowed the state to fight similar viruses.
"While I encourage all residents and visitors to continue to use precaution by draining standing water and wearing bug spray, Florida remains safe and open for business," he said in a statement.
"This year, we have already welcomed a record 30 million tourists and we look forward to welcoming more visitors to Florida this summer."
More than 1,600 Zika cases have been reported in the United States, but previously all cases have been linked to travel to affected areas or sexual contact with an infected person.
Most people infected with Zika will not have symptoms, but for those who do, the illness is usually mild. However, Zika infection during pregnancy can cause a serious birth defect of the brain called microcephaly and other severe foetal birth defects.
