At an event at the American Natural History Museum last month, Jay Varma, the Deputy Commissioner for Disease Control at the city's Health Department, noted that the biggest problem with the Zika virus is the unknown. "What we're really challenged with here is a lot of uncertainty," he said, and that uncertainty came to a head recently when the city was faced with the first case of a woman sexually transmitting Zika to her male partner. Previously, researchers thought Zika could only be transmitted from males to females, and at a press conference at the Health Department yesterday, Varma and First Deputy Commissioner Oxiris Barbot discussed how this new twist will affect how the city handles the virus.

Yesterday, the Health Department confirmed that a woman in her 20s transmitted the virus to her male partner, one day after returning from a Zika-affected region. This is the first ever confirmed case of female-to-male transmission, but the important thing, Varma noted, is that it's not a game-changer. "It's an important event, but not unexpected," he said, pointing out that researchers are still trying to figure out exactly how the virus works.

So far, 5,000 New Yorkers have been tested for the virus—309 tested positive (36 of whom are pregnant women), and only 3 of those cases were sexually transmitted, including the newest female-to-male case. Researchers are still not sure how long Zika stays in semen; whether it can be spread through saliva; or why this is the only incidence in which the virus was transmitted via vaginal fluid. Basically, Zika is still a big mystery, which is why it's so scary right now. "This is a situation where the board on which we're playing the game is completely different," Barbot said. "We're learning about how Zika behaves."

The main thing, Varma and Barbot noted, is that pregnant women should not travel to Zika-affected regions, which currently include all of Central and South America and the Caribbean. Women of reproductive age who do not plan on becoming pregnant but do travel to these countries should be on a primary form of birth control and use barrier methods like condoms. Men and women who travel to Zika-affected regions should wait two months before having unprotected sex with their partners, provided they have no symptoms.

That number goes up to six months if you did contract Zika, and officials say males who traveled to Zika-affected regions at any point should not have unprotected sex with their pregnant partners for the duration of the pregnancy. And now, the city has extended these guidelines to women with pregnant partners, since researchers aren't sure how the virus behaves in vaginal fluid and it's been proven biologically possible for woman-to-woman transmission. The Health Department also recommends that people who have traveled to Zika-affected regions do not share sex toys with their pregnant partners.

So far, the city has pledged $21 million to monitor and respond to Zika.