Zika virus. – Photo: NIAD

A report has for the first time indicated that Zika virus can be transmitted by oral sex. The study was published in The New England Journal of Medicine on June 2.

The World Health Organisation (WHO) and the Centers for Disease Control and Prevention (CDC) have clearly stated that the Zika virus has been found in semen samples and sexual transmission of the virus is possible.

The first case of sexual transmission was reported in mid April in two men who had anal sex. In January 2016, a man who returned to Dallas, Texas from Venezuela had unprotected anal sex before and after the onset of symptoms and transmitted the virus to his partner.  Transmission of the virus through vaginal sex has also been reported earlier.

Oral route

A 24-year-old woman living in Paris and who had never travelled to any of the countries where Zika virus is in circulation had sex with a man who had returned from Brazil. He was in Brazil from December 11, 2015 to February 9, 2016.

The woman had seven episodes of both vaginal sexual intercourse, without ejaculation and without the use of a condom, and oral sex with ejaculation.

She tested positive for Zika virus on February 23.  The woman had the virus both in her urine and saliva samples but not in vaginal swap samples. The man’s urine and semen samples tested positive for the virus.

Dr. Yazdan Yazdanpanah, a coauthor from the Institut National de la Santé et de la Recherche Médicale, Paris, told The New York Times that the couple was using oral sex as a method of birth control.

The study result confirms the hypothesis of sexual transmission (either oral or vaginal) of Zika virus from the man to the woman. “We cannot rule out the possibility that transmission occurred not through semen but through other biologic fluids, such as pre-ejaculate secretions or saliva exchanged through deep kissing,” they write.

Saliva sample of the man was tested only on day 10 after the onset of symptoms tested negative and not earlier. The authors say that though the virus has been detected in saliva in other people, “to our knowledge, no cases of transmission through saliva have been documented,” they note.

The CDC says a man can transmit the virus to his male or female partner through sexual intercourse — vaginal, anal, and likely, oral sex (fellatio). “At this time, there is no evidence that a woman with Zika can transmit the virus to her sex partner during vaginal sex or cunnilingus (mouth-to-vagina oral sex). There is also no evidence that Zika can be transmitted through deep kissing. Available studies have detected Zika in saliva, urine, and breast milk, but not in vaginal swabs collected from women with Zika,” the CDC notes.