New York – A New York City woman infected her male partner with Zika virus through sex, the first time female-to-male transmission of the germ to be documented.
Zika is usually spread by mosquitoes, and health officials have known for some time that men can spread it through sex. The Centers for Disease Control and Prevention reported the case on Friday and updated its advice for pregnant women.
The CDC now advises them to use protection if their sex partner has traveled to a Zika-infected region, whether the partner is a man or a woman.
The Zika virus causes only a mild illness in most people. But infection during pregnancy can lead to severe brain-related birth defects for the fetus.
While this is the first documented case of a woman spreading Zika through sex, health experts say it is not surprising because most diseases that can be spread through sex can be spread by both men and women.
On the day the New York woman returned from a trip to a Zika-infected country, she had vaginal sex with her partner, without a condom, 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.
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 traveled from a Zika outbreak area and no cases of female-to-male transmission had been reported. He tested positive for Zika.
They both are in their 20s and have recovered, a CDC official said.
Eleven countries, including the United States, have reported cases of apparent sexual transmission of Zika virus from one person to another, according to the World Health Organization.
At least 14 were people are believed to have caught it from sex with travelers. There have been no reports of mosquitoes spreading Zika in the continental United States so far.
Male-to-female transmission is considered far more likely than the other way around, experts said. One reason is that 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.
In the New York case, several factors lined up to allow the disease to spread. The couple had sex just before the woman developed symptoms, a time when the amount of virus in her body may have been particularly high. They had sex just before her period started, so there may have been a small amount of early bleeding. The man was uncircumcised, and uncircumcised men are considered at higher risk of catching sexually transmitted diseases.