The Centers for Disease Control and Prevention (CDC) has announced their first suspected case of female-to-male transmission of the Zika virus. A New York City woman infected her male partner with Zika through intercourse after she returned from travelling to a country with the disease.

The woman had vaginal sex with her partner, without a condom, on the day she returned from a trip to a Zika-infected country, health officials were told. She went to her doctor three days after her return after developing common Zika symptoms such as fever, fatigue, rash and back pain. Tests showed Zika infection, CDC reported.

Seven days after they'd had sex, her male partner developed similar symptoms. Two days later, he went to the same doctor. The doctor tested him even though he hadn't travelled from a Zika outbreak area. He also tested positive for Zika.

They are both in their 20s, but no other details about them were released, including where the woman travelled. Both have recovered, a CDC official said.

The disease is largely spread via infected mosquitoes, but has also been documented as spread via male-to-female intercourse. In adults the disease symptoms are generally mild, but Zika can cause devastating microcephaly — an unusually small head and brain — in fetuses born to women who contracted the virus while pregnant.

Health officials have cautioned pregnant women not to travel to countries with Zika, and to use "barrier methods" during sex with any partner who lives in or travels to a Zika outbreak area.

Male-to-female transmission is considered far more likely than woman to man, experts believe. The Zika virus has been found to linger in semen for more than two months, but is thought to stay in vaginal fluid no more than two weeks, No woman-to-woman sexual transmission had been reported to date.

Eleven countries, including the US, have reported cases of apparent sexual transmission of the Zika virus.

Among the more than 1,300 people in the 50 states and the District of Columbia who have been diagnosed with Zika, at least 14 likely caught it from sex with travellers. The rest became infected while travelling to Latin America, the Caribbean or other outbreak areas.

Most or all of those travellers likely were infected through mosquito bites in the countries they were visiting. There have been no reports of mosquitoes spreading Zika in the continental US so far.

The US congress has failed to pass a Zika-fighting health initiative because of continuing squabbles over abortion and Planned Parenthood funding.

A major pending concern is the upcoming Olympic games in Brazil, where thousands of babies born with microcephaly have been linked to the Zika virus. Several athletes have opted not to attend the games to protect themselves from the virus.