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How Worried You Should Be About Getting Zika From Sex

After the CDC found 14 new cases of Zika sexually transmitted from men to women in the US, an expert answered all of my paranoid questions about the virus.
February 24, 2016, 6:35pm
Photo by Flickr user "coniferconifer"

US health officials are investigating 14 new cases of Zika virus, which are thought to have been sexually transmitted. According to reports, all those infected were women—including several pregnant women—who had sex with men who traveled to infected zones. "These cases involve possible transmission of the virus from men to their sex partners," the Center for Disease Control (CDC) said in a press release. In two of the cases, sexual transmission has been confirmed; confirmation on the 12 remaining cases is pending.


Because serious birth defects are linked to the disease, the World Heath Organization has declared Zika a public health emergency. In Brazil, 49 babies born with suspected Zika-associated microcephaly, a birth defect that causes abnormal head and brain development, have died. Experts, however, have said that the threat of Zika in the US is low, due to the fact that disease is thought to be primarily carried by the Aedes aegypti mosquito that is restricted to warmer climates. Earlier this month, a couple in Dallas had the honor of being the first case of sexually exchanged Zika virus stateside and, at the time, the CDC didn't seem too worried about the method of transmission. But does the mounting number of infections passed on by sex warrant fear about love in the time of Zika?

The CDC has said that "sexual transmission may be a more likely means of transmission for Zika virus than previously considered," but Dr. Leslie Lobel, an American expat who is currently the chair of the department of microbiology, immunology and genetics at Ben Gurion University in Israel, doesn't think there's a lot to be concerned about—and he's one of the world's few people who can call themselves Ebola experts and has researched virology for over a decade. "This discovery of sexual transmission [of Zika] is not surprising," he says. "There are many viruses, even Ebola, that could be sexually transmitted potentially. Still, it's a potential risk that people need to be aware of, primarily women who want to become pregnant, might be pregnant, or are pregnant. Beyond that, the virus itself, for women who are not pregnant, even now and even in Brazil, has not caused very serious illness. It's still a mild disease."


Zika is known to cause a rash and fever, though beyond that little is known about the disease. There is currently no vaccine to prevent or medicine to treat Zika.

In terms of acquiring the disease through sexual transmission, the CDC has said that women who have sex with men are most susceptible, whether that sex results in pregnancy or not. The CDC's guidelines urge men who "reside in or have traveled to an area of active Zika virus transmission" to use condoms or abstain from sex. "In some cases [of infectious diseases], there's a greater transmission from male to female. When the virus is in a female, obviously it can be transmitted through vaginal secretions, but it would probably be more difficult for those secretions to get into the male than for the male semen to infect a female," Dr. Lobel explains.

Right now, experts still don't know how long the virus is transmittable. Dr. Lobel theorizes that men could possibly transmit the disease to sexual partners even after they stop displaying symptoms. "There are things called 'immune privilege sites,' which are organs of the body—like the eye and the testes—where the immune system really can't get there," he says. "A lot of times, when the virus is under attack by the immune system or by drugs that are being used to treat viral disease, the virus still resides in these immune privilege sites," he says. "This means that even when an infected person is clear of the disease, the virus is still replicating. So it could be that men, theoretically, are able to transmit for quite some time."

Overall, Dr. Lobel insists that the threat of Zika shouldn't keep you up at night—unless you're pregnant or traveling to a mosquito-friendly climate. "I don't think people in the United States need to be worried about this disease," he says. "Obviously, women who are pregnant or want to become pregnant need to be careful and aware of this and know what to do. Don't travel to South America or countries where there's a big outbreak right now. If your partner travels, use precaution. But other than that, I'm not really scared of this virus.

"It's eventually going to become endemic in South America as it is probably in Africa. Once it's endemic it becomes a non-issue. Most of the people who have been infected by the virus become immune, and you'll have this huge herd immunity where there can be very little transmission. That's basically it."

Everything is chill, says virology expert.