HIV transmission risk significantly increases in late-diagnosed HIV and at HIV viral load (VL) \u3e1500 copies/mL. The objective of this dissertation was to examine factors associated with HIV transmission risk potential for persons with HIV (PWH) using measures of time from HIV infection to diagnosis and trajectories of VL suppression. Additionally, we sought to determine whether a single yearly VL measure—the current standard to track the HIV epidemic in the United States—is reliable in assessing viral suppression for PWH. The first study estimated the distribution of time from HIV infection to diagnosis in Florida using a CD4 depletion model and utilized a frailty model to determine individual- and neighborhood-level factors associated with receiving a diagnosis within 40 months after HIV infection (based on the most recent median time from HIV infection to diagnosis in 2018 reported in a U.S. national study). Overall, the median time to diagnosis was 83 months and was stable during 2014-2018. Older adults, non-Hispanic Blacks (vs. non-Hispanic Whites), and heterosexual males (vs. men who have sex with men) were less likely to be diagnosed within 40 months after HIV infection. The second study examined agreement between three viral suppression measures among clients in the Miami-Dade County Ryan White Program (RWP): recent viral suppression, defined as having a suppressed VL (/mL) in the last test in 2017; maintained viral suppression, having a suppressed VL for both the first and last VL tests in 2017; and sustained viral suppression, having all VL tests in 2017 showing suppression. Recent viral suppression measures overestimated maintained and sustained viral suppression measures, by 7.0% and 10.1%, respectively. Non-Hispanic Blacks (0.88 [0.74-1.00]) and Haitians (0.87 [0.72-1.00]) had lower Gwet’s agreement coefficient scores than Hispanics (0.94 [0.87-1.00]) and non-Hispanic Whites/Others (0.93 [0.82-1.00]) across all three definitions. The third study determined the percentage of person-time spent with VL \u3e1500 copies/mL and utilized a random-effects zero-inflated negative binomial model to determine factors associated with experiencing longer time with VL \u3e1500 copies/mL for 6390 RWP clients. On average, clients spent 27.4 days per year at substantial risk of transmitting HIV. Younger age, AIDS diagnosis, and drug use in the preceding 12 months were associated with longer time spent at VL \u3e1500 copies/mL. In conclusion, a substantial number of individuals lived with HIV for a long time before their diagnosis in Florida, and on average, PWH spent nearly a month per year at substantial risk of transmitting HIV. Policies and tailored interventions targeting the specific HIV needs of underserved populations may help reduce transmission risk. Reporting viral suppression estimates using maintained or sustained viral suppression in addition to recent viral suppression may be beneficial in clinical care and for adequate monitoring of programmatic outcomes
