The first case of Zika virus that was sexually transmitted from a female to a male partner has been documented in New York City, according to the Centers for Disease Control and Prevention.

The CDC says that a woman in her twenties (who is not pregnant) had unprotected sex with a male partner on the day she returned from an area with an ongoing Zika virus transmission. The next day, she began exhibiting symptoms of Zika (fever, fatigue, a rash, back pain) and soon tested positive for Zika. Her partner, who is also in his 20s, tested positive for the virus a week later, despite not having traveled outside of the country. He had not had sex with anyone else or received any recent mosquito bites, suggesting the virus was transmitted via his partner.

Though Zika can be transmitted through sexual activity, so far the virus has only been confirmed through male-to-female sex, since Zika stays longer in semen than in vaginal fluid. The CDC has recommended that males traveling to Zika-affected regions wait eight weeks before having unprotected sex with female partners; if they've actually contracted Zika, that waiting period goes up to six months. The department will update those recommendations to include guidelines for females traveling to Zika-affected regions after studying the length of time in which Zika stays in vaginal fluid.

The CDC will also offer $50 to males who have contracted Zika to study their infected semen. As of yesterday, 40 men volunteered.

The NYC Health Department is having a press conference this afternoon to discuss the findings; we'll have more from that later.