Two Britons have caught the zika virus in Florida, according to a Public Health England report.
Since last year 229 UK travellers have tested positive for the virus, including the two who contracted it in Miami-Dade County.
Zika is carried by mosquitoes and associated with a birth defect called microcephaly, where babies are born with abnormally small heads.
Symptoms of the virus can include mild fever, skin rash, headaches and muscle or joint pain.
“The risk in Miami-Dade County is considered high and pregnant women are advised to postpone non-essential travel until after pregnancy,” Public Health England said, adding that there was a moderate risk elsewhere in Florida.
The zika epidemic started in Brazil last year and has been deemed a public health emergency by the World Health Organisation.
Other affected areas include the Caribbean, where 158 British travellers have contracted it. The Aedes aegypti mosquito, which transmits it, is not found in the UK.
People returning from affected regions are advised to practise safe sex for at least six months to avoid passing on the virus.