You might have heard that AIDS is not as deadly in Africa as it once was. Deaths from the disease have declined by a third in sub-Saharan Africa since 2005.

But the virus is actually becoming more prevalent among adolescents—particularly adolescent girls. In many African nations, teen girls are two or three times more likely to contract HIV than boys are, according to UNICEF.

Gender Distribution of HIV Among Teens, by Region

One reason is that girls in some African nations are pressured into early sexual debut and early marriage. That, combined with low rates of condom use and the possibility of multiple sex partners, increases their potential for HIV exposure over time.

And it's not just a problem facing African women: In the U.S., 84 percent of women diagnosed with HIV get it through heterosexual sex.

There are already a few options available for women who want to prevent HIV infection. Daily pills called pre-exposure prophylaxis, or PrEP, are prescribed for some people who are considered high-risk, and there are always condoms or female condoms—though many women find it hard to convince their partners to use them.