The US Centres for Disease Control and Prevention issued a Zika alert for Cuba, a day before President Barack Obama arrives on the Communist-ruled island, urging travellers to "practice enhanced precautions".
Saturday's "Alert" is the second of three levels of travel notices issued by the CDC, the highest of which is a "Warning" to avoid all non-essential travel, Efe news agency reported.
Noting that Zika, a virus spread by the Aedes aegypti mosquito, is linked to a serious birth defect of the brain known as microcephaly and "other poor pregnancy outcomes," the CDC recommended that pregnant women not travel to Cuba.
It said other travellers should take steps—such as wearing long-sleeved shirts or using insect repellent —to avoid being bitten by mosquitoes.
That US national public health institute also warned that sexual transmission of the Zika virus from a male partner was also possible and therefore encouraged travellers either to use condoms or abstain from sex.
The alert comes four days after Cuba confirmed the first case of local transmission of the Zika virus and a day before Obama makes the first trip to the island by a US president in 88 years.
Accompanied by his wife Michelle, his daughters Sasha and Malia, and his mother-in-law Marian Shields Robinson, Obama will arrive on Sunday in Havana and take part in a full programme of events through Tuesday in the Cuban capital before flying to Buenos Aires.
Cuba also has reported five imported cases of Zika to date, corresponding to travellers who contracted the virus in Venezuela and Brazil.