Health officials have suggested that pregnant women consider whether they absolutely need to travel to Florida after four people with Zika have been found to have caught the disease from local mosquitoes.
The TravelHealthPro site, run by the National Travel Health Network and Centre, has listed the risk of contracting Zika virus in Florida as "moderate".
"Pregnant women should consider postponing non-essential travel to affected areas until after the pregnancy," it says. "At present, only a zone of about 1 square mile in Miami-Dade County is considered at risk of active transmission."
The four cases in Florida are believed to be the first 'homegrown' cases of the disease being transmitted by mosquitoes living nearby, whereas other cases have been due to travel to affected areas.