The investigators aim to assess type and frequency of HIV drug resistance in adults presenting to the Infectious Diseases Institute (IDI) in Kampala, Uganda, and compare this data to patients from the Swiss HIV Cohort Study (SHCS). This study is a single-site, cross-sectional study. The Investigators' goal is to perform viral load measurements in 2750 HIV-infected patients who have been on ART for 6 months or more. Presuming a detectable viral load in 10%, resistance testing would then be performed in 250 patients on ART. All adult patients attending will be screened for enrollment. Furthermore, the investigators' goal is to perform resistance testing in 250 ART naive patients in order to detect transmitted resistance mutations. Investigators will therefore consecutively screen and enroll 250 ART naive patients who attend the clinic during the study period. For each participant, a case report form (CRF) form will be completed which includes social, as well as medical information. Investigators will ask each participant for permission to store plasma in case resistance testing must be repeated, and serum, in case of future research questions.