The Stages of HIV Infection

Figure 4 Latent and active HIV infection in macrophages.

The progress of HIV infection in adults can be divided into threeclinical phases (Figure 5):

Phase I. The number of viral RNA molecules per milliliter of blood plasma may reach more than 10 million in the first weekor so. Billions of CD4 ⁺ T cells may be infected within a couple ofweeks. Immune responses and fewer uninfected cells to targetdeplete viral numbers in blood plasma sharply within a fewweeks. The infection may be asymptomatic or cause lymphadenopathy(swollen lymph nodes).

Phase 2. The numbers of CD4 ⁺ T cells decline steadily. HIVreplication continues but at a relatively low level, probably controlledby CD8⁺ T cells and occursmainly in lymphatic tissue. Only a relatively few infected cellsrelease HIV, although many may contain viruses in latent orproviral form. There are few serious disease symptoms, but adecline in immune response may become apparent by theappearance of persistent infections by the yeast Candida albicans, which can appear in the mouth, throat, or vagina. Other conditionsmay include fever and persistent diarrhea.

Phase 3. Clinical AIDS emerges, usually within 10 years ofinfection. CD4 ⁺ T cell counts are below 350 cells/µl (200 cells/µldefines AIDS). Important AIDS indicator conditions appear,such as C. albicans infections of bronchi, trachea, or lungs;cytomegalovirus eye infections; tuberculosis; Pneumocystis pneumonia; toxoplasmosis of the brain; and Kaposi's sarcoma.

Figure 5. The progression of HIV infection

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