Assess Therapeutic Efficacy and Emergence of HIV Drug Resistance Following Initiation of TLD

Inclusion Criteria: * Receiving care at a PEPFAR-supported site. * Documentation of HIV-1 infection acceptable to the local PEPFAR-supported program to allow ART to be initiated or continued. * Ability and willingness of participant or legal guardian/representative to provide informed consent to participate in the study. * Expectation that the participant will receive care within the local PEPFAR-supported program and will be able to be followed for study evaluations for at least 6 months and ideally for 36 months. * Group 1 participants: Receipt of an NNRTI-containing first-line ART regimen from a clinic in a PEPFAR-supported country for at least 6 consecutive calendar months prior to study entry. NOTE: ART treatment gaps are allowed, but treatment gaps should not exceed 14 consecutive days in the 6 calendar months prior to study entry. * Group 1 participants: HIV-1 RNA \>1000 copies/mL obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry at any network-approved non-US laboratory that operates in accordance with Good Clinical Laboratory Practices (GCLP) and participates in appropriate external quality assurance programs. * Group 2 participants: Receipt of a boosted PI-containing second-line ART regimen from a clinic in a PEPFAR-supported country for at least 6 consecutive calendar months prior to study entry. NOTE: ART treatment gaps are allowed, but treatment gaps should not exceed 14 consecutive days in the 6 calendar months prior to study entry. * Group 2 participants: HIV-1 RNA obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry at any network-approved non-US laboratory that operates in accordance with Good Clinical Laboratory Practices (GCLP) and participates in appropriate external quality assurance programs. 1. If Group 2b reaches its enrollment target of 360 participants, the protocol team will notify sites that the following criteria will be implemented: For Group 2 participants, an HIV-1 RNA \>1000 copies/mL will need to be obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry. 2. If Group 2a reaches its enrollment target of 180 participants, the protocol team will notify sites that the following criteria will be implemented: For Group 2 participants, an HIV-1 RNA ≤1000 copies/mL will need to be obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry. * Group 4 participants: No current or prior ART treatment. NOTE: Women who received ART regimens only during pregnancy and/or breastfeeding for prevention of mother-to-child transmission but who have not taken any ART drugs for at least 6 calendar months immediately prior to study entry will be allowed. * For Group 1, 2, and 4 participants, expected initiation of TLD taken once daily within 7 days after study entry. NOTE: Group 1, 2, and 4 participants may not be on, or expected to start, RIF-containing TB treatment at the time of study entry. * For Group 3 participants already on RIF-containing TB treatment but not on TLD at study entry, expected initiation of TLD taken once daily with an additional daily dose of DTG 50 mg. This must be started within 7 days after study entry AND within 56 days after the start of RIF-containing TB treatment. These participants may be ART-naïve, or may be switching from a first- or second-line ART regimen. NOTE: For ART-naïve participants who start RIF-containing TB treatment first and then start TLD at a later date, screening must occur within 14 days before the intended TLD start date. * For Group 3 participants not already on RIF-containing TB treatment but already on TLD at study entry, receipt of TLD for at least 6 consecutive calendar months prior to study entry AND expected initiation of RIF-containing TB treatment within 7 days after study entry. * For Group 3 participants not already on RIF-containing TB treatment or TLD at study entry, expected initiation of TLD and RIF-containing TB treatment within 7 days after study entry. These participants may be ART-naïve, or may be switching from a first- or second-line ART regimen. * For Group 1 participants, HIV-1 RNA \>1000 copies/mL obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry at any network-approved non-US laboratory that operates in accordance with Good Clinical Laboratory Practices (GCLP) and participates in appropriate external quality assurance programs. * For Group 2 participants, HIV-1 RNA obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry at any network-approved non-US laboratory that operates in accordance with Good Clinical Laboratory Practices (GCLP) and participates in appropriate external quality assurance programs. 1. If Group 2b reaches its enrollment target of 360 participants, the protocol team will notify sites that the following criteria will be implemented: For Group 2 participants, an HIV-1 RNA \>1000 copies/mL will need to be obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry. 2. If Group 2a reaches its enrollment target of 180 participants, the protocol team will notify sites that the following criteria will be implemented: For Group 2 participants, an HIV-1 RNA ≤1000 copies/mL will need to be obtained as part of standard of care or with a real-time test within 12 weeks prior to study entry. Exclusion Criteria: * Weight ≤30 kg. * For participants already on ART in Groups 1, 2, and 3, known to have had an ART interruption encompassing the entire 14 day window (≥14 consecutive days) immediately prior to study entry. * For Group 3, if a participant is already taking TLD at the time of study entry, HIV-1 RNA \>1000 copies/mL within the past 9 months while taking TLD with no subsequent HIV-1 RNA ≤1000 copies/mL. * Prior enrollment in any group in this study. * For Group 3 participants, already on concomitant TLD and RIF-containing TB treatment prior to study entry. * For Group 2 participants with HIV-1 RNA \>1000 copies/mL from a host country in which treatment guidelines require a genotypic test prior to switching patients on a boosted PI-containing second-line ARV regimen to TLD, 65R RT mutation within 12 weeks prior to study entry.