Zika May Spread Through Oral Sex--And Through Kissing, Scientists Warn

Amid increasing number of Zika cases in the world, scientists are now raising the possibility that the virus may be transmitted not only through vaginal sex but also by oral sex and kissing.

In a letter to The New England Journal of Medicine, scientists cited a case in France where a 24-year-od woman was infected with the virus after having sex with her partner, a 46-year-old man who returned to Paris from Rio de Janeiro, which has the most number of infected people.

While in Brazil, the man had experienced Zika symptoms, such as fever, headache and rash, which ended when he reached France.

According to the report, the couple had sex seven times between February 11 and February 20, each involving vaginal sex without ejaculation and oral sex with ejaculation.

On February 20, the woman became ill, and both were tested for Zika on February 23. The man was said to have high levels of the virus in his semen and urine, but none in the blood and saliva. The woman had traces of the virus in her urine and saliva, and antibodies in her blood.

However, after a vaginal swab, she tested negative for the virus.

In the report, the scientists said that they "could not 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 noted that the man's saliva tested negative for the virus after he started exhibiting symptoms, although it was not tested earlier. They said that Zika has been detected in saliva, but there haven't been any cases of transmission through saliva documented yet.

"I don't think this changes anything, but it shows you how elaborate the number of avenues of possible transmission can be," Dr. William Schaffner, head of preventive medicine at Vanderbilt University Medical School, told The New York Times.

According to Schaffner, the transmission route was most likely oral sex, but he also said that it was possible that the woman got infected through pre-ejaculation during vaginal sex. It is also possible that the couple might have recalled each sex act wrongly.

But Dr. Yazdan Yazdanpanah, an infectious disease specialist at the National Institute of Health and medical Research in Paris and one of the authors of the report, said that the two were interviewed separately and their accounts matched.

Dr. John T. Brooks, an epidemiologist at the U.S. Centers for Disease Control and Prevention (CDC) studying sexually-transmitted Zika, told The New York Times that he was "not particularly surprised" on transmission by oral sex.

However, he pointed out that transmission of the virus through kissing is unlikely.

There are already confirmed cases of sexually-transmitted Zika in the United States, prompting the CDC to release prevention guidelines earlier this year.