HIV, the human immunodeficiency virus, is an often sexually-transmitted infection that attacks the body's immune system and leaves it vulnerable to disease. HIV infection can progress in stages to acquired immune deficiency syndrome (AIDS), a potentially life-threatening condition. The progression of HIV infection to an AIDS diagnosis can be slowed or prevented with medical treatment if the infection is detected early enough. Screening tests include the HIV antibody test, rapid HIV testing, HIV antibody/antigen tests, and early-detection tests. The CDC recommends at least one test for everyone aged 13 to 64. Any patient whom a physician considers to be at high risk, and anyone initiating a new sexual relationship, should be screened more frequently in accordance with a doctor's recommendations.