Clinical Guidance for Healthcare Providers for Prevention of Sexual Transmission of Zika Virus
- Zika can be sexually transmitted from a person who has Zika to his or her sex partners, even while they are not symptomatic.
- Pregnant women with sex partners who live in or traveled to an area with risk of Zika should use condoms during sex or abstain from sex for the duration of their pregnancy.
- All other couples in which a partner has been in an area with risk of Zika can also reduce the risk of sexual transmission by using condoms or abstaining from sex
- Healthcare providers should test pregnant women with symptoms of Zika (e.g., fever, rash, headache, arthralgia, conjunctivitis, and muscle pain) if they may have been exposed to Zika through sex without a condom with a person who lives in or traveled to an area with risk of Zika
- Healthcare providers should test any patients for Zika if they have symptoms and report potential sexual exposure to a partner who lives in or traveled to an area with risk of Zika, even if that partner was never sick.
Questions & Answers
What kind of sexual activity puts someone at risk for Zika if their partner is infected?
A person with Zika can transmit the virus to his or her partner(s) through vaginal sex, anal sex, and likely oral sex. The sharing of sex toys may also put someone at risk. Zika has been detected in semen, vaginal fluids, saliva, urine, and breast milk. There is no evidence at present that Zika can be transmitted through saliva during deep kissing.
There is documented evidence of sexual transmission of Zika from male-to-female, male-to-male, and female-to-male sex partners. Female-to-female sexual transmission has not yet been reported but is biologically plausible.
Are infections of same-sex partners being identified?
To date, there has been one case of male-to-male sexual transmission in the United States; none of the confirmed cases of sexual transmission have been female-to-female. However, other STDs can be passed between female sex partners, so it would not be unexpected to eventually have such a case documented. Women with Zika may pass the virus to sex partners through vaginal fluids or menstrual blood.
The use of condoms or abstinence is recommended to protect sex partners concerned about Zika. The partners of people who live in or traveled to areas with risk of Zika should be tested if they had condomless sex and develop symptoms of Zika.
Can asymptomatically infected people have Zika in genital secretions and transmit it to their sex partners?
Sexual transmission from an asymptomatically infected male has been reported. Zika virus RNA was not detected in his semen 31 days after he left an area with widespread Zika virus transmission. There is at least one probable case where Zika virus RNA was detected in the semen of an asymptomatically infected male at 39 days after he left an area with widespread Zika virus transmission. People with symptomatic illness have transmitted Zika before they had symptoms, while they had symptoms, and after symptoms resolved. We do not know how long after infection men can no longer transmit Zika sexually and whether infection in men with symptoms of illness differs from infection in asymptomatic men with Zika.
Studies are underway to help us better understand when and under what circumstances Zika can be transmitted sexually. Specifically, scientists are studying semen and vaginal secretions to understand the incidence of viral shedding, the concentrations of virus, and the duration and pattern (e.g., steady decline, intermittent on/off) of viral shedding in genital secretions of symptomatic and asymptomatic individuals.
How long can Zika be transmitted to sex partners after initial infection?
Our knowledge is growing rapidly but we don’t yet know exactly how long infected people can transmit Zika sexually. Available data are currently limited to case reports. We will have more information from studies that are underway. Detection of Zika virus RNA in semen has been reported up to 188 days after illness onset. It is important to note that the presence of Zika virus RNA does not necessarily represent the presence of infectious virus. Even so, current evidence suggests that Zika virus capable of infection persists longer in semen than in other body fluids, including vaginal fluids, urine, and blood. CDC therefore recommends that pregnant couples use condoms or abstain from sex for the entire pregnancy, if the pregnant woman’s partner had a possible Zika virus exposure. Non-pregnant couples with a partner who traveled to an area with risk of Zika should consider using condoms or abstaining from sex for:
The longer precautionary period recommended for men with Zika takes into consideration the fact that evidence of Zika (Zika virus RNA) can persist in the semen of infected men after they have recovered from illness, that we don’t yet know how long it takes for an infected man’s semen to clear the virus, and that we don’t have good evidence that Zika illness differs between infected men with symptoms and infected men who never develop symptoms. Ongoing studies are systematically examining the incidence and duration of Zika virus shedding in the genital secretions of people with both symptomatic and asymptomatic Zika infection.
How common is it for people to transmit Zika to their sex partners?
We do not know. CDC is conducting a study of men and women infected with Zika to better understand how often different body fluids, including semen and vaginal fluids, can transmit Zika. To date, the majority of documented cases of sexually transmitted Zika infection have been from men to their sex partners. The limited number of cases of sexual transmission from women to their sex partners suggests that it can occur but is less frequent than sexual transmission of Zika from men. It would not be unexpected to see more cases of sexual transmission from women to their sex partners, but at this time CDC expects most cases will continue to be reported from men to their female and male sex partners. None of the confirmed cases of sexual transmission have been female-to-female. However, other STDs can be passed between female sex partners and it would not be unexpected to eventually have such a case documented. Women with Zika may pass the virus to sex partners through vaginal fluids or menstrual blood.
Should people who have been in areas with risk of Zika take precautions to prevent sexual Zika transmission to their partners?
Yes, especially if their partner is pregnant. Zika virus infection during pregnancy can cause microcephaly and other severe fetal nervous system defects.
Men and women who have traveled to or live in an area with risk of Zika and who have a pregnant sex partner should use a condom every time they have vaginal, anal, or oral sex or abstain from sex for the duration of the pregnancy. They should also avoid sharing sex toys throughout the pregnancy. This is important even for those who are asymptomatic. Most people who are infected do not have symptoms and it is possible that an asymptomatic person can transmit Zika through sex.
Men and women who have traveled to or live in an area with risk of Zika and who have partners who are not pregnant can also use condoms consistently and correctly to protect against infection or not have sex, if they are concerned about sexually transmitting Zika. The recommended length of time for using condoms or not having sex will depend on the person’s sex and where s/he lives. People considering condoms or abstinence should weigh the personal risks and benefits, which include:
What should I tell patients concerned about getting Zika through sex?
Only people with sex partners who traveled to or live in an area with risk of Zika are at risk for getting Zika virus through sex. Sexual transmission of Zika is of greatest concern for pregnant women with partners who have had, or are at risk for, Zika virus infection.
To be effective, condoms must be used correctly from start to finish, every time during vaginal, anal, and oral sex.
When is Zika testing recommended to identify possible sexual transmission cases?
Zika virus testing has been recommended to establish a diagnosis of infection. Zika virus testing is recommended for people who may have been exposed to Zika through sex and who have Zika virus symptoms. Zika virus testing is also recommended for pregnant women who have symptoms of Zika and have recent exposure to Zika, for asymptomatic pregnant women with ongoing exposure to Zika, and for pregnant women whose fetus has birth defects potentially associated with Zika identified on ultrasound.
At this time, testing a person’s blood, urine, or genital secretions to determine their potential risk of sexually transmitting Zika virus is not recommended for the following reasons:
First, a negative blood test or antibody test could be falsely reassuring. This can happen when:
Second, we currently have limited understanding of Zika virus shedding in genital secretions, or of how to interpret the results of tests of semen or vaginal fluids. Zika shedding in these secretions may be intermittent, in which case a person could test negative at one point but still carry the virus and shed it again in the future. Studies are underway to better understand the pattern of Zika shedding in genital secretions.
For more information on diagnostic testing for Zika, see Testing for Zika.
What is the role for STD/HIV Programs in the Zika response?
STD and HIV programs have expertise in patient education, communication, and condom promotion and distribution efforts that may be relevant to preventing sexual transmission of Zika virus. CDC encourages state and local programs to work with their state health officials and connect concerned STD/HIV clients with possible sexual exposure to Zika to primary care or reproductive health providers who can offer counseling and follow up.
- Page last reviewed: December 13, 2017
- Page last updated: December 13, 2017
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