Quick Answer

AIDS develops when HIV has severely damaged the immune system, typically after years without treatment. It is the most advanced stage of HIV infection, defined by a very low CD4 cell count or the presence of certain opportunistic infections. With modern antiretroviral therapy, HIV can be controlled so that AIDS does not develop.

  • HIV attacks CD4 cells, which coordinate the immune response.
  • Without treatment, CD4 counts drop over years, leading to AIDS.
  • AIDS is diagnosed when CD4 count falls below 200 cells/mm³.
  • Certain infections, like Pneumocystis pneumonia, also indicate AIDS.
  • Antiretroviral therapy can keep HIV at undetectable levels, preventing AIDS.
  • Undetectable viral load means HIV cannot be transmitted sexually (U=U).

Context Most Pages Skip

HIV is a retrovirus that infects and destroys CD4 cells, the immune system's key coordinators. Over time, if the virus is not suppressed, the immune system weakens, leaving the body vulnerable to infections and cancers. AIDS is the final stage of this progression, not a separate virus. The timeline varies widely - some people progress in a few years, others in a decade or more. The key point is that AIDS is preventable: with consistent antiretroviral therapy, HIV replication is halted, CD4 counts can recover, and the immune system remains functional.

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⚕️ This page is educational and does not replace advice from a licensed clinician. If you may have been exposed to an STI, get tested — most infections are manageable, and many are fully curable.

Sources & Further Reading

Figures reflect CDC surveillance and WHO estimates; they are population statistics, not personal risk predictions.