AIDS
Meaning of AIDS: Living with HIV and having AIDS are not the same thing, and with effective treatment most people never reach the second.
Definition of AIDS
AIDS, short for acquired immunodeficiency syndrome, is the advanced stage of infection with HIV, the human immunodeficiency virus. The virus destroys CD4 T cells, which coordinate the immune response, and once enough of them are gone the body can no longer control organisms and cancers it would ordinarily hold in check. AIDS names that stage, not the infection as a whole.
How is AIDS distinguished from HIV infection?
Two things can define it, and either is enough. The first is a fall in CD4 T cells below a set threshold, measured by a blood test. The second is the appearance of a condition that essentially only occurs once immune defenses have collapsed, whatever the cell count happens to be that day. Those conditions are listed and include Pneumocystis pneumonia, thrush spreading down the esophagus, cryptococcal meningitis, toxoplasmosis of the brain, disseminated mycobacterial infection, Kaposi sarcoma, certain lymphomas and invasive cervical cancer.
| HIV infection | AIDS | |
|---|---|---|
| What it describes | Presence of the virus, at any stage | The advanced stage of that same infection |
| Immune system | May be near normal for many years | Severely depleted CD4 T cells |
| How it is established | Antibody or viral tests | CD4 count below a threshold, or a defining illness |
What is an opportunistic infection?
An opportunistic infection is caused by an organism that a working immune system contains without effort, often one already living harmlessly in or on the body. Given the opportunity of weakened defenses, it multiplies and causes disease. The pattern of which organisms appear tracks fairly closely with how far the CD4 count has fallen, which is why the same illnesses recur across very different populations.
Has the outlook changed?
Substantially. Combination antiretroviral therapy suppresses viral replication, CD4 counts recover, and progression to AIDS has become uncommon wherever treatment is available and started before major damage is done. Someone who once met the criteria keeps that classification in surveillance records even after their immune system recovers, so the label describes a stage reached rather than a permanent state of health. Sustained suppression of the virus to undetectable levels in the blood also prevents sexual transmission to a partner.
Also known as
Used in a sentence
The patient's history of an opportunistic infection was consistent with a diagnosis of AIDS.
Good to know
AIDS describes the advanced stage of HIV infection defined by significant immune damage, and it is not interchangeable with HIV infection itself, since many people living with HIV never progress to that stage.