Mums-to-be who are travelling to Florida are being advised to postpone their trip due to the Zika virus.
It comes after four patients in the US state tested positive for the virus - and appeared to be the first cases not linked to travel outside mainland USA.
As a result Public Health England has now updated its travel advice.
The health body has said the risk in the state on the south-east coast of the United States is moderate, while many countries in South America, including Olympic host Brazil, is high.
The Zika virus has been associated with a birth defect called microcephaly, which results in children being born with abnormally small heads and brain damage.
The updated travel advice reads: "The risk in Florida is considered moderate based on the number and spread of cases and their demonstrated ability to implement effective control measures for similar diseases such as dengue - a virus transmitted by the same mosquito.
"Pregnant women should consider postponing non-essential travel to affected areas until after the pregnancy.
"At present, only a zone of about one square mile in Miami-Dade County is considered at risk of active transmission."
A total of 53 people have been treated in the UK for the infection.
Three of those were diagnosed in Huddersfield Royal Infirmary and Calderdale Royal Hospital in West Yorkshire
Since the Zika epidemic began in 2015, nearly 5,000 cases of microcephaly have been recorded in affected regions.
In February the World Health Organisation declared the epidemic an international public health emergency.
Experts have predicted that the current epidemic may not last more than another two to three years due to the high number of infections leading to "herd immunity".
This is when such a high proportion of a population develop immunity to a virus or microbe that the infectious agent runs out of available hosts.