Human Immunodeficiency Virus (HIV) is the virus that causes AIDS. It attacks the human immune system. Over time (and without effective treatment), HIV gradually destroys the body's defenses against disease, leaving it vulnerable to many infections and cancers that would not normally develop.
Even without treatment, some people with HIV infection have no symptoms at all, others have mild health problems, and still others have severe health problems associated with AIDS.
Acquired Immune Deficiency Syndrome (AIDS) is a late stage of HIV infection. By the time a diagnosis of AIDS is made, HIV will already have seriously damaged the body's immune system. Often, a person with an AIDS diagnosis will already have a life-threatening infection or cancer.
Before the use of effective treatment, it commonly took 10 years or more from the time of initial HIV infection to a diagnosis of AIDS. On average, it would take another two to four years before death. However, new treatments are radically slowing the destruction of the immune system caused by HIV and lengthening life expectancy. Some people with HIV infection may never develop AIDS.
Information courtesy Public Health – Seattle & King County.