Update: Interim Guidance for Preconception Counseling and Prevention of Sexual Transmission of Zika Virus for Persons with Possible Zika Virus Exposure — United States, September 2016

Review of Evidence

Zika virus infection during pregnancy is a cause of congenital microcephaly and serious brain abnormalities (4). The risk for adverse pregnancy outcomes associated with maternal Zika virus infection around the time of conception is unknown. To date, there have been no published reports of adverse pregnancy outcomes after periconceptional Zika virus infection. Infections with other viruses (e.g., cytomegalovirus, rubella, parvovirus) around the time of conception have been associated with congenital infection and adverse pregnancy outcomes, although the exact timing of infection relative to conception was sometimes uncertain (5–9).

Zika virus is transmitted primarily through the bite of Aedes aegypti mosquitoes. Zika virus can also be transmitted through sex without a condom. The risk for sexual transmission of Zika virus from a person infected with Zika virus remains unknown. Most reported sexual transmissions have been from persons with symptomatic Zika virus infections, including from men to female sex partners (10–12), from a man to his male sex partner (13), and from a woman to her male sex partner (14). Two new reports describe one presumed and one more definitive case of sexual transmission from men with asymptomatic Zika virus infection to female sex partners (15,16). Sexual transmission of Zika virus has been associated with condomless anal sex and vaginal sex and possibly also with fellatio (17). Among reported cases of sexually transmitted Zika virus infection, the longest reported period between sexual contact that might have transmitted Zika virus and symptom onset was 32–41 days (based on an incubation period of 3–12 days) (18).

Data on the detection of Zika virus RNA in semen can inform estimates of the periods during which sexual transmission might occur. However, detection of Zika virus RNA in semen might not indicate the presence of infectious virus and thus the potential for sexual transmission. Reports indicate that concentrations of detectable Zika virus RNA in semen decrease after infection (17,19–28). Zika virus RNA was detected in semen of five men more than 90 days after symptom onset, with the longest period of reported detection 188 days after symptom onset (20,26,29,30). Culture is considered the gold standard for demonstrating the presence of replicative and thus infectious virus, and among four published reports of Zika virus cultured from semen, virus was reported in semen up to 69 days after symptom onset (17,19,21,31). Culture methods varied in these studies and additional studies are needed to confirm the presence of infectious virus in semen.

New data on the persistence of Zika virus RNA in serum and whole blood might have implications, both for sexual transmission of Zika virus and for fetal exposure to Zika virus. Zika virus RNA has been detected in the serum of nonpregnant persons up to 11–13 days after symptom onset (32); in the serum of pregnant women, Zika virus RNA has been detected up to 10 weeks after symptom onset (33,34). Zika virus RNA was detected in whole blood of a nonpregnant person up to 58 days after symptom onset followed by a negative result at 79 days; however, Zika virus could not be cultured at 58 days (35). Experience with other flaviviruses suggests that if a person’s immune system has activated an antibody response, viral transmission (i.e., through blood transfusion) is unlikely (36). Detection of Zika virus RNA in blood might not indicate the presence of infectious virus, and thus the potential risk for maternal-fetal Zika virus transmission periconceptionally is unknown.

Guidance for Preconception Counseling and Prevention of Sexual Transmission

CDC is updating its guidance on timing of conception after possible Zika virus exposure and prevention of sexual transmission of Zika virus. CDC continues to evaluate all available evidence and update recommendations as new data become available. Most of the recommendations for preconception counseling and prevention of sexual transmission are dependent on whether persons live in or travel to areas of active Zika virus transmission.^¶ As of September 26, 2016, 59 countries and U.S. territories reported active Zika virus transmission. The Florida Department of Health identified two areas of Miami-Dade County with active local mosquito-borne Zika virus transmission; as of September 20, 2016, only one remains an area of active transmission (37). Updates on areas with active Zika virus transmission are available online at http://www.cdc.gov/zika/geo/index.html.

For Couples Planning to Conceive Who Do Not Live in Areas with Active Zika Virus Transmission. Health care providers should discuss couples’ travel plans in preconception counseling. Women and men who are planning to conceive in the near future should consider avoiding nonessential travel to areas with active Zika virus transmission.

Women who have had possible Zika virus exposure through travel or sexual contact and do not have ongoing risks for exposure should wait at least 8 weeks from symptom onset (if symptomatic) or last possible exposure (if asymptomatic) to attempt conception. Women who wait at least 8 weeks to conceive might have an increased likelihood that Zika virus no longer presents a risk for maternal-fetal transmission.

CDC now recommends that men with possible Zika virus exposure, regardless of symptom status, wait at least 6 months from symptom onset (if symptomatic) or last possible exposure (if asymptomatic) before attempting conception with their partner. CDC previously recommended that men with possible Zika virus exposure who were asymptomatic wait at least 8 weeks from last possible exposure. The updated recommendation minimizes the likelihood that periconceptional sexual transmission will result in fetal exposure to Zika virus. The recommendation to wait at least 6 months for asymptomatic men is based on the range of time after symptom onset that Zika virus RNA has been detected in semen of symptomatic men and the absence of definitive data that the risk for sexual transmission differs between symptomatic and asymptomatic men. Zika virus has not been definitively cultured from semen more than 3 months after symptom onset. It is unknown whether detection of Zika virus RNA in semen indicates presence of infectious virus and the potential for transmission. Current recommendations provide couples planning to conceive with periods that, based on existing data, are expected to minimize risk for Zika virus transmission to an uninfected partner. Studies are underway to better understand the persistence of infectious Zika virus in semen and the associated risk for sexual transmission of the virus. Given that limited data are available, some couples in whom a partner had possible Zika virus exposure might choose to wait longer or shorter than the recommended period to conceive, depending on individual circumstances (e.g., age, fertility, details of possible exposure) and risk tolerance. For example, after consultation with their health care provider, symptomatic persons with negative test results who received testing in the appropriate time window and in accordance with the testing algorithm (38) might choose not to wait to conceive.

For Couples Who Want to Conceive, in Which One or Both Partners Live in Areas with Active Zika Virus Transmission. Women and men who reside in areas with active Zika virus transmission and who experience symptoms of Zika virus disease should be tested for Zika virus infection (38). Men with results that indicate recent Zika virus or unspecified flavivirus infection should wait at least 6 months from symptom onset to attempt conception with their partner; women with results that indicate recent Zika virus or unspecified flavivirus infection should wait at least 8 weeks from symptom onset to attempt conception. Persons who have had symptoms of Zika virus disease with negative Zika virus test results should talk with their health care provider about timing of conception in the setting of ongoing risk for possible exposure.

Persons living in an area with active Zika virus transmission should be counseled on the possible risk for Zika virus infection during the periconception period. CDC has developed tools to assist health care providers with preconception counseling (39). Health care providers should provide counseling about the potential consequences to the fetus associated with Zika virus infection during pregnancy, such as microcephaly and other serious brain abnormalities. Women and men should discuss their reproductive life plans** with their health care provider, in the context of potential and ongoing Zika virus exposure. Health care providers should review factors that might influence pregnancy timing (e.g., unknown duration of Zika virus outbreak, fertility, age, reproductive history, medical history, personal values and preferences). For couples who choose to conceive, health care providers should stress use of mosquito bite prevention strategies^†† while attempting pregnancy and during pregnancy. Health care providers should counsel couples who decide to wait to attempt conception about strategies to prevent unintended pregnancy, including the most effective contraceptive methods (i.e., long-acting reversible contraception) and provide contraception or referral to appropriate providers for contraception care (40).

Special Considerations for Women Undergoing Fertility Treatment. Zika virus transmission through assisted reproductive technology has not been reported. However, transmission through gametes or embryos is theoretically possible. Recommendations for sexually intimate couples with Zika virus infection or possible Zika virus exposure undergoing fertility treatment with their own gametes and embryos should follow the testing and timing recommendations as described above; recommendations might need to be adjusted depending on individual circumstances. The Food and Drug Administration has issued guidance to reduce the risk for Zika virus transmission by donated human cells, tissues, and cellular and tissue-based products, including reproductive tissues (41).

For Couples Who Are Not Pregnant and Are Not Planning to Become Pregnant in the Near Future. Couples in whom the man or woman has had possible Zika virus exposure who want to maximally reduce their risk for sexually transmitting Zika virus to the uninfected partner should use condoms consistently and correctly or abstain from sex for at least 6 months for men or 8 weeks for women after symptom onset (if symptomatic) or last possible Zika virus exposure (if asymptomatic). Some couples might choose to use condoms or abstain from sex for a shorter or longer period than recommended depending on individual circumstances and risk tolerance. Couples should be advised that correct and consistent use of condoms reduces the risk for other sexually transmitted infections.

Health care providers should discuss strategies to prevent unintended pregnancy with couples who do not want to become pregnant. Safety, effectiveness, availability, and acceptability should be considered when choosing a contraceptive method (42). Patients should be counseled to use the most effective contraceptive method that can be used correctly and consistently. Long-acting reversible contraception, including contraceptive implants and intrauterine devices, provide highly effective reversible options.

For Pregnant Women and Their Partners. Pregnant women living in areas without active Zika virus transmission should be advised to avoid nonessential travel to areas with active transmission. Persons who have traveled to or live in an area with active Zika virus transmission and whose partner is pregnant should be advised to consistently and correctly use condoms during sex or abstain from sex for the duration of the pregnancy. These actions reduce the risk for sexual transmission of Zika virus during pregnancy. Health care providers should ask pregnant women about their own and their sex partner’s history of travel to areas with active Zika virus transmission. Pregnant women with possible Zika virus exposure, either through sex or through traveling to or living in an area with active Zika virus transmission, should be tested for Zika virus infection in accordance with CDC’s “Updated Interim Pregnancy Guidance: Testing and Interpretation Recommendations for a Pregnant Women with Possible Exposure to Zika Virus” (http://www.cdc.gov/zika/pdfs/testing_algorithm.pdf), including pregnant women with possible sexual exposure whose sex partner has had no symptoms of Zika virus disease. Further guidance for care of pregnant women with possible Zika virus exposure has been published (3).

Zika Virus Testing

Persons with possible Zika virus exposure who have symptoms of Zika virus disease should receive testing in accordance with CDC interim guidance: “Algorithm for U.S. Testing of Symptomatic Individuals” (38). CDC does not recommend Zika virus testing of nonpregnant persons with possible Zika virus exposure who do not have symptoms of Zika virus disease, including persons who are planning to attempt conception, or to assess the risk for sexual transmission of Zika virus. Zika virus testing for this purpose remains of uncertain value, because current understanding of the duration and pattern of shedding of Zika virus in reproductive tissues is limited. Information on the performance of serologic Zika virus testing remains limited, with falsely positive tests resulting in avoidable stress and expense and falsely negative tests providing false reassurance and possibly leading to inadvertent fetal exposure to Zika virus.