The World Health Organization says that men and women returning from any area where the Zika virus is circulating should practise safe sex for at least 6 months to avoid the risk of spreading the disease.
The advice applies even if a person has no symptoms.
It comes a few weeks after doctors discovered the virus in the sperm of an Italian man 6 months after he first had Zika symptoms.
Zika is spread in bodily fluids. The main risk of catching the disease is from infected mosquitoes via bites.