What is AIDS?
AIDS stands for acquired immunodeficiency syndrome:
A - Acquired. This condition is acquired, meaning that a person becomes infected with it.
I - Immuno. HIV affects a person's immune system, the part of the body that fights off germs such as bacteria or viruses.
D - Deficiency. The immune system becomes deficient and does not work properly.
S - Syndrome. A person with AIDS may experience other diseases and infections because of a weakened immune system.
AIDS is the most advanced stage of infection caused by HIV. The names HIV and AIDS can be confusing because both terms describe the same disease. Most people who are living with HIV do not have AIDS. And most people with HIV will not develop AIDS if they start treatment (with medicines called antiretroviral therapy or ART) soon after becoming infected. A person living with HIV is said to have AIDS when their immune system becomes so weak it can't fight off certain kinds of infections and cancers, such as PCP (a type of pneumonia), KS (Kaposi sarcoma, a type of cancer that affects the skin and internal organs), wasting syndrome (involuntary weight loss), memory impairment, or tuberculosis.
Even without one of these infections, a person living with HIV is diagnosed with AIDS if their immune system weakens, as indicated by the number of CD4 cells. But, again, it is important to remember that most people with HIV will not develop AIDS if they start treatment soon after becoming infected.