A person with HIV infection is infected by the human immunodeficiency virus. HIV slowly destroys the body's immune system, which is responsible for fighting infection in the body.

AIDS is the result of an HIV infection that has damaged the immune system. AIDS may develop within months of the initial HIV infection, or AIDS may take years to develop. Antiviral medications can prolong the progression to AIDS for years. Worldwide, about 38 million people are infected with HIV.