Wastewater Sample Site Selection to Estimate Geographically Resolved Community Prevalence of COVID-19: A Sampling Protocol Perspective

Wastewater monitoring for virus infections within communities can complement conventional clinical surveillance. Currently, most SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) clinical testing is voluntary and inconsistently available, except for a few occupational and educational settings, and therefore likely underrepresents actual population prevalence. Randomized testing on a regular basis to estimate accurate population-level infection rates is prohibitively costly and is hampered by a range of limitations and barriers associated with participation in clinical research. In comparison, community-level fecal monitoring can be performed through wastewater surveillance to effectively surveil communities. However, epidemiologically defined protocols for wastewater sample site selection are lacking. Herein, we describe methods for developing a geographically resolved population-level wastewater sampling approach in Jefferson County, Kentucky, and present preliminary results. Utilizing this site selection protocol, samples (n = 237) were collected from 17 wastewater catchment areas, September 8 to October 30, 2020 from one to four times per week in each area and compared to concurrent clinical data aggregated to wastewater catchment areas and county level. SARS-CoV-2 RNA was consistently present in wastewater during the studied period, and varied by area. Data obtained using the site selection protocol showed variation in geographically resolved wastewater SARS-CoV-2 RNA concentration compared to clinical rates. These findings highlight the importance of neighborhood-equivalent spatial scales and provide a promising approach for viral epidemic surveillance, thus better guiding spatially targeted public health mitigation strategies. Plain Language Summary The SARS-CoV-2 virus, which causes COVID-19, is shed in the stool of infected persons. Samples collected from public sewers can be used for anonymous community monitoring to identify COVID-19 "hot spots" that are not subject to the many limitations of clinical testing records, which are the standard method of COVID-19 surveillance. Here, we describe methods for developing a sewer system sampling approach at the community scale by selection and sampling of wastewater from street lines, pumping stations, and treatment facilities in Jefferson County, Kentucky. Our preliminary data indicates that our sampling design allows for much higher spatial surveillance than the county scale, with fewer limitations than surveillance based on clinical testing records. This work outlines a viable approach to guide targeted public health response strategies for cities by taking advantage of wastewater sampling.