In the red light district in Mbarara, a city in western Uganda known in part for sex tourism, a sex worker named Lisa Mutoni insists on using condoms when men enter her room, to protect her against HIV and other infections.

The problem: Some try to remove or tear the condom while having sex.

She takes HIV-prevention medication called PrEP, or preexposure prophylaxis, which can come in the form of daily pills or periodic injections.