The study team therefore proposes to carry out a cross-sectional study in a large public HIV out-patient clinic in which patients who are routinely monitored with both CD4 count and viral load measurements are compared with patients who are routinely monitored with CD4 counts measurement only. Individuals who have detectable viral load after 36 months of ARV therapy in each of the above patient categories shall undergo a structured interview and HIV genotypic testing, particularly to look for TAMs. The presence of TAMs in each instance shall be documented.