Distributed via the CDC Health Alert Network
February 23, 2016, 14:15 EST (2:15 PM EST)
CDCHAN-00388

Summary: The Centers for Disease Control and Prevention (CDC) recently published recommendations for protecting people against sexual transmission of Zika virus (1). As stated in that report, information about possible sexual transmission of Zika virus was based on one published report of transmission from a man to a woman, one published report in which Zika virus was detected in semen of a man with hematospermia, and one case of possible sexual  transmission then under investigation in Texas. An additional case of Zika virus detected in semen in a man was reported after the CDC recommendations were published (2).  As of February 23, 2016, CDC and state public health departments are investigating 14 additional reports of possible sexual transmission of the virus, including several involving pregnant women. While additional investigations are being completed, CDC is issuing this HAN 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.

Background

CDC is working with state, local, and US territorial public health departments, US Government agencies, and international partners in response to outbreaks of Zika virus disease (Zika) in multiple territories and countries in the Americas. Accumulating evidence links maternal Zika virus infection with congenital microcephaly, miscarriages, and other adverse fetal outcomes (3). In addition, there are reports of a possible association with Guillain-Barré syndrome (4). No vaccine or specific antiviral drug is currently available to prevent or treat Zika.

Zika virus is spread primarily by the bite of infected Aedes species mosquitoes (most commonly, Aedes aegypti). In areas where Zika virus transmission is ongoing, people should follow precautions to prevent mosquito bites (http://www.cdc.gov/zika/prevention/). Sexual transmission of Zika virus also can occur and is of particular concern during pregnancy. In early February 2016, the Dallas County Department of Health and Human Services announced an occurrence of sexually transmitted Zika infection (5). On February 5, 2016, following the confirmation of this Texas sexual transmission event, CDC published interim guidelines for preventing sexual transmission of Zika virus (1).

As of February 23, 2016, CDC and state public health departments are investigating 14 additional reports of possible sexual transmission of the virus, including several events involving possible transmission to pregnant women. In two of these new suspected sexual transmission events that have been investigated to date, Zika virus infection has been confirmed in women whose only known risk factor was sexual contact with an ill male partner who had recently travelled to an area with local Zika virus transmission; testing for the male partners is pending. For four additional suspected sexual transmission events, preliminary laboratory evidence (IgM antibody test) is available for the women, but confirmatory testing is still pending. For eight suspected events, the investigation is ongoing. In all events for which information is available, travelers reported symptom onset within 2 weeks prior to their non-traveling female partner’s symptom onset.

Because these reports suggest sexual transmission may be a more likely means of transmission for Zika virus than previously considered, CDC is issuing this HAN Advisory to underscore the importance of adhering to the interim guidance published on February 5 and outlined below. The recommendations, which apply to men who reside in or have traveled to areas with active Zika virus transmission (http://wwwnc.cdc.gov/travel/notices/) and their sex partners, will be revised as more information becomes available.

Recommendations for men and their pregnant partners

Men who reside in or have traveled to an area of active Zika virus transmission who have a pregnant partner should abstain from sexual activity or consistently and correctly use condoms during sex (i.e., vaginal intercourse, anal intercourse, or fellatio) for the duration of the pregnancy. Pregnant women should discuss their male partner’s potential exposures to mosquitoes and history of Zika-like illness (http://www.cdc.gov/zika/symptoms) with their health care provider; providers can consult CDC’s guidelines for evaluation and testing of pregnant women (6).

Recommendations for men and their nonpregnant sex partners

Men who reside in or have traveled to an area of active Zika virus transmission who are concerned about sexual transmission of Zika virus might consider abstaining from sexual activity or using condoms consistently and correctly during sex. Couples considering this personal decision should take several factors into account. Most infections are asymptomatic, and when illness does occur, it is usually mild with symptoms lasting from several days to a week; severe disease requiring hospitalization is uncommon. The risk for acquiring vector-borne Zika virus in areas of active transmission depends on the duration and extent of exposure to infected mosquitoes and the steps taken to prevent mosquito bites (http://www.cdc.gov/zika/prevention). After infection, Zika virus might persist in semen when it is no longer detectable in blood; studies to determine the duration of persistence in semen are not yet completed.

Accumulating evidence of sexual transmission suggests that exposure to Zika virus includes unprotected sexual contact with a symptomatic male partner who resides in or has traveled to an area of active Zika virus transmission. Zika virus testing is currently recommended to establish a diagnosis of infection in exposed persons with signs or symptoms consistent with Zika virus disease, and may be offered to asymptomatic pregnant women with possible exposure to Zika virus (6). However, interpretation of results is complex, and health care providers should contact their state, local, or territorial health department for assistance with arranging testing and interpreting results. At this time, testing of exposed, asymptomatic men for the purpose of assessing risk for sexual transmission is not recommended. Sexual transmission of Zika virus from infected women to their sex partners has not been documented, nor has transmission from persons who are asymptomatically infected.  Sexual transmission of many infections, including those caused by other viruses, is reduced by consistent and correct use of latex condoms.

As we learn more about the incidence and duration of seminal shedding from infected men and the utility and availability of testing in this context, recommendations to prevent sexual transmission of Zika virus will be updated.

References

1. Oster AM, Brooks JT, Stryker JE, et al. Interim Guidelines for prevention of sexual transmission of Zika virus — United States, 2016. MMWR Morb Mortal Wkly Rep 2016;65:120–121. http://www.cdc.gov/mmwr/volumes/65/wr/mm6505e1.htm
2. Atkinson B, Hearn P, Afrough B, et al. Detection of Zika virus in semen [letter]. Emerg Infect Dis. 2016 May [cited February 22, 2016].http://dx.doi.org/10.3201/eid2205.160107
3. Martines RB, Bhatnagar J, Keating MK, et al. Evidence of Zika virus infection in brain and placental tissues from two congenitally infected newborns and two fetal losses — Brazil, 2015. MMWR Morb Mortal Wkly Rep. 2016;65 (Early Release)(06):1-2. http://www.cdc.gov/mmwr/volumes/65/wr/mm6506e1.htm?s_cid=mm6506e1_e.  Published February 19, 2016.
4. European Centre for Disease Prevention and Control. Rapid risk assessment: Zika virus epidemic in the Americas: potential association with microcephaly and Guillain-Barré syndrome – 10 December 2015. http://ecdc.europa.eu/en/publications/Publications/zika-virus-americas-association-with-microcephaly-rapid-risk-assessment.pdf. Published 2015. Accessed Feb 1, 2016.
5. Dallas County Health and Human Services.  DCHHS reports first Zika virus case in Dallas County acquired through sexual transmission. February 2, 2016. http://www.dallascounty.org/department/hhs/press/documents/PR2-2-16DCHHSReportsFirstCaseofZikaVirusThroughSexualTransmission.pdf
6. Oduyebo T, Petersen EE, Rasmussen SA, et al. Update: interim guidelines for health care providers caring for pregnant women and women of reproductive age with possible Zika virus exposure—United States, 2016. MMWR Morb Mortal Wkly Rep 2016;65.http://www.cdc.gov/mmwr/volumes/65/wr/mm6505e2.htm?s_cid=mm6505e2_e

For More Information

• General information about Zika virus and disease: http://www.cdc.gov/zika/
• Zika virus information for clinicians: http://www.cdc.gov/zika/hc-providers/index.html
• Protection against mosquitoes: http://wwwnc.cdc.gov/travel/yellowbook/2016/the-pre-travel-consultation/protection-against-mosquitoes-ticks-other-arthropods
• Travel notices related to Zika virus: http://wwwnc.cdc.gov/travel/notices
• Information about Zika virus for travelers and travel health providers: http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-diseases-related-to-travel/zika
• HAN Advisory:  Recognizing, managing, and reporting Zika virus infections in travelers returning from Central America, South America, the Caribbean, and Mexico.  January 15, 2016.  http://emergency.cdc.gov/han/han00385.asp
• Pan American Health Organization PAHO): http://www.paho.org/hq/index.php?option=com_content&view=article&id=11585&Itemid=41688〈=en
• Approximate distribution of Aedes aegypti and Ae. albopictus mosquitoes in the United States:
  http://www.cdc.gov/chikungunya/resources/vector-control.html