With 14 New Cases, CDC Rethinks Zika Sex Transmission

February 23rd, 2016

By Gary Evans, Senior Staff Writer

Conceding that sex "may be a more likely means of transmission for Zika virus than previously considered,” the Centers for Disease Control and Prevention issued a health advisory today reporting 14 new cases of possible sexual transmission -- including several involving pregnant women.

While the cases are under investigation, CDC issued the advisory as "a strong reminder to state, local, and US territorial public health departments, clinicians, and the public to be aware of and adhere to current recommendations for preventing sexual transmission of Zika virus, particularly for men with pregnant partners. These recommendations may change as more information becomes available."

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, the CDC reports. Testing of the male partners is still pending. In 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,” the CDC announced today. “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.”

As with Ebola, the CDC finds itself outflanked by an emerging infection that is behaving a little differently than predicted based on previous experience. The primary focus on mosquito bites could now be overwhelmed by the unfolding evidence that sexual transmission of Zika might not be a rare event -- dogma that was based on the scant evidence of sexual transmission since the virus emerged in the Uganda in 1947. The emergence of -- and certainly the prevalence of -- microcephaly birth defects apparently caused by Zika also appears to have little precedent.

As a result of the new sex cases, the CDC is reiterating its Feb. 5, 2016 recommendations to prevent sexual transmission of Zika, which advise in part that men with a pregnant sex partner who reside in or have traveled to an area of active Zika virus transmission 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. In addition, 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. Providers should consult CDC’s guidelines for evaluation and testing of pregnant women.

The 14 new cases under investigation follow the recent confirmation of the first case of Zika virus infection in a non-traveler in the continental United States, which was linked to sexual contact with an infected partner in Dallas.

“Although sexual transmission of Zika virus infection is possible, mosquito bites remain the primary way that Zika virus is transmitted,” the CDC stated. “Because there currently is no vaccine or treatment for Zika virus, the best way to avoid Zika virus infection is to prevent mosquito bites.”

Despite the new cases, the CDC continues to recommend that couples with no pregnancy considerations or risk issues might "consider" safe sex or abstinence if a male partner has traveled to an area where Zika is being transmitted. "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,” the CDC states. 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, the CDC reports.

The March issue of Hospital Infection Control & Prevention contains a trio of stories examining the latest Zika developments, including combating the spread of the virus via sexual transmission. Additionally, the March issue of Hospital Employee Health contains a story about protecting pregnant healthcare workers from contracting the virus.