This manuscript summarizes the break-out session held on the epidemiology of disease expression of koala retrovirus (KoRV) in koalas (Phascolarctos cinereus) at the Koala Conservation Workshop: The koala and its retroviruses: implications for sustainability and survival held at San Diego Zoo, April 17–18, 2013. The goals of this break-out session were to develop and prioritize specific research goals related to KoRV epidemiology, to identify actions, and to determine the responsible parties and timelines. Identified areas for epidemiologic research include studies in both wild and captive populations. For wild populations, baseline estimates of incidence and prevalence that account for potential biases in surveillance are needed. Landscape-level studies that determine whether KoRV contributes to the decline or stability of wild populations are also a priority. Captive populations with high-quality health data and management records can provide opportunities to identify factors associated with disease expression. These populations may also be pivotal in understanding the clinical importance of different KoRV subtypes.