AIDS stands for Acquired Immune Deficiency Syndrome.
An HIV-positive person receives an AIDS diagnosis after developing one of the CDC-defined AIDS indicator illnesses. An HIV-positive person can also receive an AIDS diagnosis on the basis of certain blood tests (CD4 counts) and may not have experienced any serious illnesses. A positive HIV test does not mean that a person has AIDS. A diagnosis of AIDS is made by a physician according to the CDC AIDS Case Definition.
Over time, infection with HIV (Human Immunodeficiency Virus) can weaken the immune system to the point that the system has difficulty fighting off certain infections. These types of infections are known as opportunistic infections. Many of the infections that cause problems or that can be life-threatening for people with AIDS are usually controlled by a healthy immune system. The immune system of a person with AIDS has weakened to the point that medical intervention may be necessary to prevent or treat serious illness.