Anyone returning from areas hit by the virus should practise safe sex for six months.
The World Health Organization on Tuesday toughened its advice on preventing the spread of Zika, saying anyone returning from areas hit by the virus should practise safe sex for six months afterwards.
The updated guidelines mean the UN health body's recommendations regarding sexual transmission are now the same whether or not people are showing symptoms of the virus.
"WHO recommends practising safer sex or abstinence for a period of six months for men and women who are returning from areas of active transmission... to prevent Zika virus infection through sexual transmission," the agency said.
The WHO suggested in June that men should avoid sex or use protection for eight weeks after coming back from visits to affected places if they did not show symptoms.
"Mounting evidence has shown that sexual transmission of Zika virus is possible and more common than previously assumed," the WHO said in guidelines released Tuesday.
Zika is primarily a mosquito-borne virus that causes no symptoms in four out of five of those affected.
But if pregnant women are infected, they face a higher risk of having a baby with head and brain defects, a condition known as microcephaly.
The WHO also recommended on Tuesday that people in Zika-hit areas be offered a full range of contraception options in order "to make an informed choice about whether and when to become pregnant."