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The Centers for Disease Control (CDC) issued an official U.S. travel warning over Zika outbreak. See this CBS News story for more information.

Meanwhile, The Centers for Disease Control has also confirmed that the Zika virus can be transmitted through sexual contact. This means that your partner may be bitten by a mosquito and become infected with the Zika virus and then he could infect you. Most people who become infected with the Zika virus don’t get sick so your partner might not show any symptoms. If you’re trying to get pregnant, it’s very important to protect yourself and your partner from mosquito bites. And, if you know you’re pregnant, you and your partner need to use a condom the proper way, every time you have vaginal, anal, or oral (mouth-to-penis) sex. Or, you should not have sex while you are pregnant. 

Questions and Answers about Sexual Transmission of the Zika Virus

What kind of sexual activity puts someone at risk for Zika if their partner is infected?

A man with Zika can transmit the virus to his sex partner(s) through sexual intercourse, including vaginal and anal sex, and likely, oral sex (fellatio). At this time, there is no evidence that a woman with Zika can transmit the virus to her sex partner(s) during vaginal sex or cunnilingus (mouth-to-vagina oral sex). There is also no evidence that Zika can be transmitted through deep kissing. Available studies have detected Zika in saliva, urine, and breast milk, but not in vaginal swabs collected from women with Zika.

Can asymptomatic infected men have Zika in semen and transmit it to their sex partners?

We don’t know. In known cases of sexual transmission, the men had Zika virus symptoms. From these cases, we know the virus can be spread when the man has symptoms, before symptoms start, and after symptoms resolve.

Studies are underway to help us better understand when and under what circumstances Zika can be transmitted sexually. Specifically, scientists are examining whether there are differences between the semen of men with symptomatic and asymptomatic Zika infection in terms of the incidence of viral shedding, the concentrations of virus in semen, and the duration and pattern (e.g. steady decline, intermittent on/off) of viral shedding.  

How long can Zika be transmitted to sex partners after initial infection?

We don’t know. Zika virus has been detected in semen up to 62 days after the onset of symptoms. The CDC therefore recommends that men who have been diagnosed with Zika should use condoms or not having sex for at least 6 months. Ongoing studies are examining the incidence and duration of Zika virus shedding in the semen of men with symptomatic and asymptomatic Zika infection.

Should men take precautions to prevent Zika transmission to female and male sex partners?

Yes. Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects. Men who live in or travel to areas with Zika should protect their sex partners from sexually transmitted Zika, particularly if their partner is pregnant or may become pregnant.

Men with pregnant partners should be counseled to use condoms every time they have vaginal, anal, or oral (mouth-to-penis) sex or abstain from sex for the duration of the pregnancy.  Following this advice is important for all men at risk of Zika infection, including men who do not have symptoms of illness because the infection is most often asymptomatic and we do not yet know the extent to which asymptomatically infected men shed infectious Zika virus in their semen.

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