Projections of wastewater as an indicator of COVID-19 cases in corrections facilities: a modelling study

Abstract Background Although prison facilities are not fully isolated from the communities they are located within, the majority of the population is confined and requires high levels of health vigilance and protection. This study sought to examine the dynamic relationship between facility level wastewater viral RNA concentration and probability of at least one positive COVID-19 case within the facility. Methods The study period was January 11, 2021 through May 12, 2023. Wastewater samples were collected and analyzed for SARS-CoV-2 (N1) and pepper mild mottle virus (PMMoV) three times per week across 14 prison facilities in Kentucky (USA). Confirmed positive clinical case reports were also provided. A hierarchical Bayesian spatial-temporal model with a latent lagged process was developed. Findings We modeled a facility-specific SARS-CoV-2 (N1) normalized by PMMoV wastewater ratio associated with at least one COVID-19 facility case with an 80% probability. The ratio differs among facilities. Across the 14 facilities, our model demonstrates an average capture rate of 94·95% via the N1/PMMoV threshold with p ts ≥ 0·5. However, it is noteworthy as the p ts threshold is set higher, such as at 0·9 or above, the model’s average capture rate reduces to 60%. This robust performance underscores the model’s effectiveness in accurately detecting the presence of positive COVID-19 cases of incarcerated people. Interpretation The findings of this study provide a correction facility-specific threshold model for public health response based on frequent wastewater surveillance.