The Centers for Disease Control and Prevention (CDC) and state public health departments are now investigating 14 new reports of possible sexual transmission of Zika virus, including several involving pregnant women. In two of the new suspected sexual transmission events, Zika virus infection has been confirmed in women whose only known risk factor was sexual contact with an ill male partner who had recently traveled to an area with local Zika virus transmission; testing for the male partners is still pending.
For four additional suspected sexual transmission events, preliminary laboratory evidence (IgM antibody test) is available for the women, but confirmatory tests are pending. For eight other suspected events, the investigation is ongoing. In all events for which information is available, travelers were men and reported symptom onset was within 2 weeks before the non-traveling female partner’s symptoms began. Like previously reported cases of sexual transmission, these cases involve possible transmission of the virus from men to their sex partners. At this time, there is no evidence that women can transmit Zika virus to their sex partners; however, more research is needed to understand this issue.
Although sexual transmission of Zika virus infection is possible, mosquito bites remain the primary way that Zika virus is transmitted. Because there currently is no vaccine or treatment for Zika virus, the best way to avoid Zika virus infection is to prevent mosquito bites.
Because these new reports suggest sexual transmission may be a more likely means of transmission for Zika virus than previously considered, CDC issued a Health Advisory Notice (HAN) today to underscore the importance of adhering to the interim guidance published on February 5.
The CDC’s February 5 interim guidance includes:
Recommendations for pregnant women and men with pregnant sex partners who live in or have traveled to Zika-affected areas:
- Pregnant women and their male sex partners should discuss the male partner’s potential exposures and history of Zika-like illness with the pregnant woman’s health care provider (http://www.cdc.gov/zika/symptoms/). Providers should consult CDC’s guidelines for evaluation and testing of pregnant women.
- Men with a pregnant sex partner who reside in or have traveled to an area of active Zika virus transmission and their pregnant sex partners should use condoms the right way every time during sex (vaginal, anal, or oral) or abstain from sexual activity for the duration of the pregnancy. Using latex condoms the right way every time reduces the risk of sexual transmission of many infections, including those caused by other viruses.
Recommendations for non-pregnant women, and men with non-pregnant sex partners who live in or have traveled to Zika-affected areas:
- Couples in which a man resides in or has traveled to an area of active Zika virus transmission who are concerned about sexual transmission of Zika virus may consider using condoms the right way every time during sex or abstaining from sexual activity.
- Couples may consider several factors when making this complex and personal decision to use condoms or not have sex:
- Zika virus illness is usually mild. An estimated 4 out of 5 people infected never have symptoms; when symptoms occur they may last from several days to one week.
- The risk of Zika infection depends on how long and how much a person has been exposed to infected mosquitoes, and the steps taken to prevent mosquito bites while in an affected area.
- The science is not clear on how long the risk should be avoided. Research is now underway to answer this question as soon as possible. If you are trying to get pregnant, you may consider testing in discussion with your health care provider.