In 2001, the United Nations General Assembly Special Session (UNGASS) endorsed the ABC approach to preventing HIV infection. The ABC approach to behaviour change gives three clear messages for preventing the transmission of HIV. ABC stands for: Abstain from having sexual relations or, for youth, delay having sex; Be faithful to one uninfected partner; and use Condoms consistently and correctly.
Sometimes D, for Drugs, is added to the message, referring to intravenous drug use and recreational use of alcohol, which can increase the likelihood of unsafe sex. Some also refer to ABC+, which includes the message to get tested and treated for STIs (which increase the risk of transmission of HIV in unprotected sex). Each component of the ABC message should be presented in a comprehensive and balanced way. (See Chapter 4.)See Source