Two months after Maripaz Callejas’ husband died of AIDS, she was diagnosed with HIV. One doctor told her that she would be dead within five years.

In Maripaz’s home country, El Salvador, many new HIV infections occur as a result of unprotected sex between couples who are married or living together. WHO estimates that globally as many as half of all HIV-positive people in long-term relationships have HIV-negative partners – forming what are known as serodiscordant couples. It is estimated that half of people living with HIV still do not know that they are infected, and, like Maripaz, many people in relationships do not know their partner’s status.