Quick Answer
AIDS is caused by untreated HIV infection. HIV is a retrovirus that attacks and destroys CD4 immune cells; without antiretroviral therapy, the immune system weakens over years, leading to AIDS. Modern treatment can suppress HIV to undetectable levels, stopping progression and preventing transmission (U=U).
- HIV is a retrovirus that infects CD4 T-cells, the immune system's helpers.
- Without treatment, HIV slowly destroys CD4 cells, leading to AIDS over 8–10 years on average.
- AIDS is diagnosed when CD4 count falls below 200 cells/mm³ or specific opportunistic infections occur.
- Antiretroviral therapy can halt progression and achieve an undetectable viral load.
- People with undetectable HIV cannot transmit the virus to others (U=U).
- AIDS is the advanced stage of HIV infection, not a separate virus.
Context Most Pages Skip
HIV (human immunodeficiency virus) causes AIDS by systematically dismantling the immune system. The virus targets CD4 T-cells, which coordinate the body's defense against infections. Over months to years of untreated infection, the number of these cells declines, leaving the body vulnerable to illnesses that a healthy immune system would normally control. This progression is not inevitable—modern antiretroviral therapy can keep HIV in check, preventing the immune collapse that defines AIDS. Understanding the mechanism helps clarify why early diagnosis and treatment are critical.
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Sources & Further Reading
- CDC — Sexually Transmitted Infections
- CDC STI Treatment Guidelines
- WHO — Sexually transmitted infections fact sheet
- MedlinePlus — Sexually Transmitted Diseases
Figures reflect CDC surveillance and WHO estimates; they are population statistics, not personal risk predictions.