According to a new Health Department study, women who had unprotected sex with bisexual men accounted for most of the new female HIV cases in New York last year. Of the 647 women diagnosed with HIV in 2012, 480 had sex with infected men.

During the early years of the HIV/AIDS epidemic, many women contracted HIV from having sex with men who carried the deadly virus from drug use. Or the women abused drugs themselves. But in recent years, the transmission of HIV to women has changed. Women are contracting HIV from men who’ve had sex with other men who are infected.

The Centers for Disease Control said that “Men who engage in sex both with men and women can acquire HIV from a male partner and then transmit the virus to female partners.” Unfortunately for the women, they may not have know of their male partners’ sexual activity.