Zika virus is a flavivirus closely related to dengue, West Nile, and yellow fever viruses. Although spread is primarily by Aedes species mosquitoes, two instances of sexual transmission of Zika virus have been reported (1,2), and replicative virus has been isolated from semen of one man with hematospermia (3). On February 5, 2016, CDC published recommendations for preventing sexual transmission of Zika virus (4). Updated prevention guidelines were published on February 23.* During February 6–22, 2016, CDC received reports of 14 instances of suspected sexual transmission of Zika virus. Among these, two laboratory-confirmed cases and four probable cases of Zika virus disease have been identified among women whose only known risk factor was sexual contact with a symptomatic male partner with recent travel to an area with ongoing Zika virus transmission. Two instances have been excluded based on additional information, and six others are still under investigation. State, territorial, and local public health departments, clinicians, and the public should be aware of current recommendations for preventing sexual transmission of Zika virus, particularly to pregnant women (4). Men who reside in or have traveled to an area of ongoing Zika virus transmission and have a pregnant partner should abstain from sexual activity or consistently and correctly use condoms during sex with their pregnant partner for the duration of the pregnancy (4).

Zika virus disease is an arboviral disease and a nationally notifiable condition in the United States (5). For the purposes of this report, a confirmed or probable case of sexually transmitted Zika virus disease was defined as an illness meeting the confirmed or probable arbovirus surveillance case definition in a person whose only known risk factor was sexual contact with a partner who recently traveled to an area with ongoing Zika virus transmission (6).

During February 6–22, 2016, two confirmed and four probable cases of Zika virus sexual transmission were reported to CDC by health officials from multiple states. Median patient age was 22.5 years (range = 19–55 years), and several women were pregnant. In all cases where type of sexual contact was documented, the contact included condomless vaginal intercourse and occurred when the male partner was symptomatic or shortly after symptoms resolved. Three illustrative cases are presented.

Case 1. In mid-January, immediately after returning to the United States from a 10-day trip to the Caribbean, a man developed illness with fever, arthralgia, bilateral conjunctivitis, and a maculopapular, pruritic rash. The illness lasted 6 days. No hematospermia or prostatitis was noted. On the 1st or 2nd second day of illness, he had condomless vaginal intercourse with his female partner. The woman developed a febrile illness 13–14 days after sexual contact, with rash, conjunctivitis, and myalgia. Zika virus RNA was detected in the woman’s serum by reverse transcription-polymerase chain reaction (RT-PCR) assay. Test results for the man are pending. The woman had no recent history of travel outside of the continental United States, and local mosquito-borne transmission of Zika virus was not considered possible; the vectors that transmit the virus are not present or active where she lives, based on the location and current temperatures.

Case 2. In late January, a man returned to the United States after a 4-week trip to Central America. The same day, he developed fever, arthralgia, generalized pruritus, myalgia, and eye discomfort. He had condomless vaginal intercourse with his female partner several times during the following 8 days. Ten days after the man’s return, his female partner developed fever, pruritic rash, arthralgia, eye pain, photophobia, headache, vomiting, and myalgia. Zika virus infection in the woman was confirmed by RT-PCR testing of serum. Serum collected from the man tested positive for Zika virus immunoglobulin M (IgM) antibodies; confirmation is pending. The woman had no recent history of travel outside the continental United States, and current local mosquito-borne transmission of Zika virus was not considered possible where she lives.

Case 3. In mid-January, a man returned from Central America with fever, rash, arthralgia, conjunctivitis, headache, and myalgia. His symptoms began 3 days earlier and persisted until approximately 3 days after his return. On the day of his return, he had sexual contact with his female partner. Ten days later, the woman developed rash, arthralgia, conjunctivitis, and myalgia. Serum collected from the woman tested positive for Zika virus IgM; confirmation is pending. Test results for the man are pending. The woman had no recent history of travel outside of the continental United States, and current local mosquito-borne transmission of Zika virus was not considered possible where she lives.

References

1. Foy BD, Kobylinski KC, Chilson Foy JL, et al. Probable non-vector-borne transmission of Zika virus, Colorado, USA. Emerg Infect Dis 2011;17:880–2. CrossRef PubMed
2. Dallas County Health and Human Services. DCHHS reports first Zika virus case in Dallas County acquired through sexual transmission. February 2, 2016. Dallas, TX: Dallas County Health and Human Services; 2016. http://www.dallascounty.org/department/hhs/documents/February2016Newsletter.pdf.
3. Musso D, Roche C, Robin E, Nhan T, Teissier A, Cao-Lormeau VM. Potential sexual transmission of Zika virus. Emerg Infect Dis 2015;21:359–61. CrossRef PubMed
4. 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;65:120–1. CrossRef PubMed
5. Council of State and Territorial Epidemiologists. 2015 National Surveillance Case Definition for Arboviral diseases, neuroinvasive and non-neuroinvasive. Atlanta, GA: Council of State and Territorial Epidemiologists; 2015. http://wwwn.cdc.gov/nndss/conditions/arboviral-diseases-neuroinvasive-and-non-neuroinvasive/case-definition/2015/
6. Pan American Health Organization. Countries and territories with autochthonous Zika virus transmission in the Americas. Washington, DC: Pan American Health Organization; 2016. http://www.paho.org/hq/index.php?option=com_content&view=article&id=11603&Itemid=41696&lang=en
7. Meaney-Delman D, Hills SL, Williams C, et al. Zika virus infection among US pregnant women travelers—August 2015–February 2016. MMWR Morb Mortal Wkly Rep 2016;65.
8. 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;65:122–7. CrossRef PubMed
9. Atkinson B, Hearn P, Afrough B, et al. Detection of Zika virus in semen[letter]. Emerg Infect Dis 2016;22. Epub, February 11, 2016. CrossRef