Prevention is the best strategy for reducing the human and economic toll from HIV/AIDS. To have the largest impact on the HIV epidemic, CDC utilizes a comprehensive approach to HIV prevention. Comprehensive HIV prevention is a broad term that incorporates surveillance, research, prevention interventions and evaluation. CDC’s surveillance and research activities help to better define and understand the HIV/AIDS epidemic across the nation. CDC’s prevention interventions and capacity building efforts are based on behavioral, laboratory and medical science and work to contain the spread of HIV and AIDS. Program evaluation and policy research and development assess intervention effectiveness and refine prevention approaches.