That means anyone who travels to a country where Zika is spreading should take precautions to protect their sexual partner upon returning home - regardless of gender.
Though the case is not surprising from a medical standpoint, he said, it does bolster the public's understanding of the virus and viral transmission beyond mosquitoes. Although Zika is typically spread via mosquito bites, there have been reports of transmission from male partners to female or other male partners.
The new finding has prompted CDC to update its advice in a report issued on Friday. This summer, we urge people to consider the risks that travel may pose due to the growing spread of Zika, especially if you are or your partner is pregnant or trying to get pregnant. Seven days the two had sex, the woman's partner also developed similar symptoms and visited the same doctor. They had vaginal sex and did not use a condom.
But in most cases, symptoms of infection Zika are mild and go unnoticed.
Zika is more frequently transmitted by mosquito bites.
"As up to 80% of patients infected with ZIKV (Zika virus) remain asymptomatic, the level of sexual transmission could play a more important role than expected in the overall dynamic of ZIKV circulation", French researchers wrote in the journal Eurosurveillance, according to Forbes. There have been no reports of the virus spreading from female to female so far.
At the moment, there's not enough evidence to show that sexual transmission goes "beyond a pair of partners", Brooks said.
Every new and unusual discovery about Zika appears to ratchet up concern about the virus. But it's also true that four out of five people who come down with Zika have no symptoms, so experts admit that the numbers could be much higher.
The real priority remains preventing transmission to a developing fetus, he said.
The case was discovered in New York City during a routine investigation by the health department, which identified a woman in her 20s who reported she had engaged in a single event of sexual intercourse with a man on the same day she had returned from traveling to an undisclosed area with ongoing Zika transmission. The doctor suspected sexual transmission of the virus and alerted the health department.
CDC is now updating recommendations for sexually active people in which the couple is not pregnant or concerned about pregnancy and for people who want to reduce personal risk of zika infection through sex.
To date, there haven't been reported cases of woman-to-woman sexual transmission of the virus.