<s>[INST] How is AIDS diagnosed? [/INST] Symptoms such as fever, weakness, and weight loss may be a sign that a person’s HIV has advanced to AIDS. However, a diagnosis of AIDS is based on the following criteria:

A drop in CD4 count to less than 200 cells/mm3. A CD4 count measures the number of CD4 cells (CD4 T lymphocyte) in a sample of blood.

OR
The presence of certain opportunistic infections.
Although an AIDS diagnosis indicates severe damage to the immune system, HIV medicines can still help people at this stage of HIV infection. Source: NIH. Link: https://hivinfo.nih.gov/understanding-hiv/fact-sheets/hiv-and-aids-basics. Field: Infectious Disease. Disease: HIV </s>