And There You Have It, the First Case of a Woman Giving Zika to a Man Through Sex

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Photo: Charles Thatcher

Doctors knew that the Zika virus could be sexually transmitted, but until now they’d only seen cases where an infected man passed it to his partner. That all changed today.

The Centers for Disease Control and Prevention reported that a woman in New York City had unprotected sex with a male partner the day she returned from a country where Zika is spreading. The report doesn’t name the country. She didn’t develop symptoms until the next day and they included fever, rash, back pain, and swelling of the extremities.

After feeling sick for three days, she went to her primary-care provider who sent blood and urine samples for testing. They found that she had an active Zika infection. She is not pregnant.

One week after they’d had sex, the man started having symptoms — specifically fever, rash, joint pain, and pink eye. He went to the same doctor and tests showed he also had Zika. The man had not traveled outside of the United States in the past year and had no other recent sexual partners, nor did he remember getting any mosquito bites in the week before getting sick. The pair had vaginal intercourse only, no oral or anal sex.

This case raises the prospect of a new chain of transmission in men who haven’t traveled to an area with local Zika transmission but could unsuspectingly contract the virus and pass it to other sexual partners.

Experts don’t know how long the virus could persist in vaginal fluids, but a recent study in primates found detectable levels of Zika up to seven days after exposure. The virus can live for a fairly long time in semen: Researchers have detected it at 62 days after onset.

Current health guidelines do say that couples who want to get pregnant should use condoms for eight weeks if either the man or the woman has been to a country where Zika is spreading — even if they don’t have symptoms — because of the risk of Zika-related birth defects. But even if you’re not trying to get pregnant, this case suggests that wrapping it up after a trip can benefit your fellow citizens.