The COVID-19 pandemic and the resulting stay-home restrictions are likely to drastically impact alcohol use, due to the resulting psychological distress, anxiety, boredom, and social isolation. We propose here to examine changes in alcohol use and the impact on antiretroviral (ART) adherence in ongoing cohorts of people with HIV (PWH) with histories of alcohol use during and after the pandemic in the US (Boston) and Uganda (Mbarara). In the US, there has been a surge in alcohol sales, weekday drinking, and references to alcohol use on the internet. The impact of the COVID-19 restrictions in Uganda is not yet known. There are anecdotal reports of decreased drinking due to low accessibility of alcohol, but drinking may rebound when restrictions are lifted. PWH have high levels of alcohol use and other mental health co-morbidities, and therefore may be at high risk for increases or relapses in any setting. Research is hence urgently needed to quantify pandemic- related changes in alcohol use among PWH with heavy alcohol use in various settings. In addition, alcohol use is a consistently strong risk factor for poor antiretroviral (ART) adherence and poor viral suppression; changes in alcohol use are associated with poor HIV viral control; and the impact of the stay-home measures on medication adherence is unknown. Social desirability and recall bias impede investigations using self-report of alcohol and medication adherence, but drug levels and direct metabolites of alcohol consumption serve as objective markers, yielding quantitative results for dose-response investigations, with long half-lives for retrospective measurement. Thus, we will measure prior alcohol use using alcohol metabolite phosphatidylethanol (PEth) in dried blood spots (DBS) (measuring 2-3 weeks' alcohol use) and ethyl glucuronide (EtG) in hair (measuring 1-3 months' alcohol use), as well as ART concentrations in hair (measuring weeks to months' ART), to supplement self-report. We will leverage ongoing cohorts that are part of the NIAAA-funded URBAN ARCH consortium, as well as the UCSF Hair Analytic Laboratory (HAL), with vast experience measuring ART in hair, to adapt existing laboratory protocols to hair EtG testing, and to develop automated DBS processing for PEth. We aim to (1) determine the proportion of drinkers with regular heavy alcohol use before, during, and after stay-home restrictions among PWH in Uganda and the US (n=125 each), and characterize changes in drinking in each cohort; (2) examine whether ART levels in hair and viral suppression rates change from pre-COVID to after stay-home restrictions are lifted, and the role of changing alcohol use; and (3) adapt existing HAL ART hair assay protocols for analysis of EtG for the above aims, and to develop and validate automated DBS processing to create high-throughput PEth testing. This work will advance our understanding of the impact of the COVID-19 pandemic on alcohol use and its role in ART adherence and viral suppres...