UNAIDS considers gay men and other men who have sex with men, sex workers, transgender people, people who inject drugs and prisoners and other incarcerated people as the five main key population groups that are particularly vulnerable to HIV and frequently lack adequate access to services.

The UNAIDS 2016–2021 Strategy calls for bold action to Fast-Track the AIDS response. It incorporates a human rights-based approach to development and aims to leave no one behind in the AIDS response. The strategy recognizes sexual and reproductive health and rights issues, calls for comprehensive sexuality education and the removal of punitive laws, policies and practices that block an effective AIDS response, including travel restrictions and mandatory testing, and those related to HIV transmission, same-sex sexual relations, sex work and drug use.

In 2016, outside of sub-Saharan Africa, key populations and their sexual partners accounted for 80% of new HIV infections. Even in sub-Saharan Africa, key populations accounted for 25% of new HIV infections in 2016.