Zika May Be Transmitted By Oral Sex, Scientists Have Found

ST. CROIX — In a letter to the New England Journal of Medicine on Friday, scientists raised the possibility that the Zika virus can be transmitted by oral sex — even kissing — and described one such case in France.

The case, a single confirmation in France, may seem insignificant, but scientists now believe that sexual transmission is an important driver of the Zika epidemic in the Americas, with cases being reported in 10 countries where no mosquitoes carry the virus, including France, Germany, Italy, Portugal and New Zealand.

Currently in the U.S. Virgin Islands, there are 24 known cases of the virus: 15 in St. Croix, 8 in St. Thomas and 1 in St. John. The Department of Health reported May 3 that two pregnant women have been infected, but D.O.H. did not reveal how.

In the French, case revealed through the letter, a 46-year-old man returned to Paris from Rio de Janeiro on Feb. 10, shortly after experiencing Zika symptoms in Brazil — rash, fever, headache — that had just ended after arriving in France.

He had sex with a 24-year-old partner seven times between Feb. 11 and Feb. 20, each involving vaginal sex without ejaculation and oral sex with ejaculation, according to the letter.

The woman fell ill on Feb. 20. Both were tested for Zika infection on Feb. 23. The man had high levels of the virus in his semen and urine, but none in his blood or saliva. The woman had the virus in her urine and saliva, and antibodies to the virus in her blood. But a vaginal swab was negative for the infection.

“These data support the hypothesis of sexual transmission (either oral or vaginal) of Zika from [the infected man to the woman], reads the letter. “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. The saliva of the man tested negative on day 10 after the onset of his symptoms, but it was not tested earlier. Zika has been detected in saliva, but, to our knowledge, no cases of transmission through saliva have been documented.”

The two were using oral sex as a form of birth control, said Dr. Yazdan Yazdanpanah (via New York Times), an infectious disease specialist at the National Institute of Health and Medical Research in Paris and one of the report’s authors.

“I don’t think this changes anything, but it shows you how elaborate the number of avenues of possible transmission can be,” said Dr. William Schaffner, head of preventive medicine at Vanderbilt University Medical School.

According to the Times, Dr. William agreed that the most likely transmission route was oral sex, although he said it was possible that the woman was infected by pre-ejaculate during vaginal sex, or that the couple’s recollections of each sex act were imperfect.

Dr. John T. Brooks, an epidemiologist at the Centers for Disease Control and Prevention studying sexual transmission of the Zika virus, said he was “not particularly surprised” to see transmission that was probably by oral sex.

Transmission through kissing is unlikely, Dr. Brooks told The Times.

“Casual kissing has got to be safe because, if it weren’t, don’t you think we’d see a lot more Zika? Every mom who kissed her baby would pass it on,” he said. “To be sure, we’d have to look for deep kissing in the absence of sexual contact, and that’s hard to find.”