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New York Reports First Female-to-Male Zika Transmission Via Sex

Finding raises new concerns about disease virulence

Public health officials have identified the first reported occurrence of female-to-male sexual transmission of Zika virus, according to the Centers for Disease Control and Prevention (CDC).

A routine investigation by the New York City Department of Health and Mental Hygiene (DOHMH) identified a nonpregnant woman in her 20s who reported she had engaged in a single event of condomless vaginal intercourse with a male partner the day she returned to New York City from travel to an area with ongoing Zika virus transmission. Seven days after intercourse, the woman’s male partner, also in his 20s, developed fever, a maculopapular rash, joint pain, and conjunctivitis.

The woman had a headache and abdominal cramping while in the airport awaiting her return to New York. The following day (day 1), she developed fever, fatigue, a maculopapular rash, myalgia, arthralgia, back pain, swelling of the extremities, and numbness and tingling in her hands and feet. In addition, on day 1, the woman began menses that she described as heavier than usual. On day 3 she visited her primary care provider, who obtained blood and urine specimens. Zika virus RNA was detected in both serum and urine by real-time reverse transcription–polymerase chain reaction (rRT-PCR). The results of serum testing for anti-Zika virus immunoglobulin M (IgM) antibody were negative using the CDC Zika IgM antibody capture enzyme-linked immunosorbent assay (Zika MAC-ELISA).

Seven days after sexual intercourse, the woman’s male partner developed symptoms of Zika virus infection. Three days after the onset of his symptoms, the man sought care from the same primary care provider who had diagnosed Zika virus infection in his female partner. The provider suspected sexual transmission of Zika virus and contacted the DOHMH to seek testing for the male partner. That same day, urine and serum specimens were collected from the man. Zika virus RNA was detected in urine but not in serum by rRT-PCR testing. Zika virus IgM antibodies were not detectable by the CDC Zika MAC-ELISA assay. The CDC Arbovirus Disease Branch confirmed all rRT-PCR results for urine and serum specimens from both partners.

During an interview with the DOHMH on day 17, the man confirmed that he had not traveled outside the United States during the year before his illness. He also confirmed a single encounter of condomless vaginal intercourse with his female partner (the patient) after her return to New York City and reported that he did not engage in oral or anal intercourse with her. The man reported that he noticed no blood on his uncircumcised penis immediately after intercourse that could have been associated either with vaginal bleeding or with any open lesions on his genitals. He also reported that he did not have any other recent sexual partners or receive a mosquito bite within the week preceding his illness.

The timing and sequence of events support female-to-male Zika virus transmission through condomless vaginal intercourse, according to the CDC. The woman likely was viremic at the time of sexual intercourse because her serum, collected three days later, had evidence of Zika virus RNA by rRT-PCR. Virus present in either vaginal fluids or menstrual blood might have been transmitted during exposure to her male partner’s urethral mucosa or undetected abrasions on his penis. Recent reports document detection of Zika virus in the female genital tract, including vaginal fluid. A study in nonhuman primates detected Zika virus RNA in the vaginal fluid of three nonpregnant females up to seven days after subcutaneous inoculation, and Zika virus RNA was detected in specimens from a woman’s cervical mucous, genital swab, and endocervical swab collected three days after illness onset, using an unspecified RT-PCR test.

The new case represents the first reported occurrence of female-to-male sexual transmission of Zika virus, according to the CDC. Current guidance to prevent sexual transmission of Zika virus is based on the assumption that transmission occurs from a male partner to a receptive partner. The CDC recommends ongoing surveillance to determine the risk for transmission of Zika virus infection from a woman to her sexual partners.

Source: CDC; July 15, 2016.

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