CDC Reports Additional Mode of Zika Transmission

The Centers for Disease Control and Prevention (CDC) recently reported that the Zika virus can be transmitted from an infected man to a sex partner though anal sex. Other case reports have confirmed that the Zika virus can be transmitted sexually from an infected male to female sex partners through vaginal sex, but this is the first report confirming the transmission of the virus through anal sex.

The Zika virus causes microcephaly and other birth defects in infants, and has been linked to other outcomes such as Guillain-Barré syndrome. The known modes of transmission are from mother to child and from an infected male to a female sex partner through vaginal sex. In January 2016, the Dallas County Health and Human Services (DCHHS) investigated a reported case of transmission from a male who had travelled to an area of active Zika virus transmission, to his noninfected male partner, who had remained in the United States.

According to the report, after returning home to Dallas, Texas, from a 1-week trip to Venezuela, the male developed a fever, rash on his upper body and face, and conjunctivitis that lasted 3 days. One day before his symptom onset, and one day after, the male had unprotected anal sex with his male partner. One week later, the male partner developed a fever, myalgia, headache lethargy and malaise and subsequently “developed a slightly pruritic rash on his torso and arms, small joint arthritis of his hands and feet, and conjunctivitis.” While the symptoms resolved, both males visited their primary care provider for evaluation. Several days after symptom onset, serum specimens were collected from both patients and Zika virus infection was confirmed.

Although the Aedes aegypti mosquito is found in Dallas, stateside infection was ruled out since the winter temperatures recorded in the area during the time of infection were not high enough to warrant mosquito activity.

According to the CDC, there have been at least five other cases of sexually transmitted Zika virus infection: all male-to-female transmission involving vaginal sex. Since sexual transmission through both vaginal and anal sex is an emerging mode of transmission for Zika virus infection, health care practitioners are urged to report any cases of sexual transmission to public health agencies. These emerging modes of transmission might contribute to more infections than was first anticipated and the reporting of cases to public health agencies can help inform recommendations to prevent further infections.