Final answer:
AIDS is diagnosed when the CD4 count drops below 200 cells/μl, which can take about 8 years without treatment. This stage signifies severe immunodeficiency, and although there is no cure for HIV, antiretroviral therapies can control the disease progression.
Step-by-step explanation:
AIDS is defined as a CD4 count <200 cells/μl and typically takes about 8 years to reach this point without treatment. In a healthy individual, CD4+ T cell counts are approximately 1,000 per microliter of blood, but when a person is infected with HIV and cannot mount an effective immune response, CD4 counts drop steadily. When the count falls below 200, the risk for opportunistic diseases increases, signaling the advancement to AIDS. Although there is currently no cure for HIV, modern antiretroviral therapies can effectively control the progression of the disease, significantly prolonging the clinical latency stage and preventing the onset of AIDS.
Without treatment, the decline in CD4 helper T cells leads to severe impairment of adaptive immune functions and vulnerability to opportunistic infections. Monitoring of CD4 T cell levels is done using flow cytometry, which helps in managing treatment plans. Stage 2, or clinical latency, may last a decade or more, with CD4 T cell counts between 200 and 499 cells/μl. However, Stage 3, or AIDS, is recognized when the CD4 T cell count drops below 200 cells/μl or when opportunistic illnesses like Pneumocystis pneumonia and rare cancers such as Kaposi's sarcoma emerge.