Predictive Values of Whole Campus Wastewater Surveillance for SARS-CoV-2

Abstract

Screening university wastewater for SARS-CoV-2 emerged as an attractive method to provide ancillary data to bolster detection of viral circulation, as it had the potential to detect the presence of asymptomatic cases or cases that are part of the campus community but not the student population. Our objective was to evaluate the positive and negative predictive values of wastewater screening for COVID-19 cases. We developed and undertook a pilot wastewater screening program for the Fall semester of 2020. Homogenized wastewater influent was collected once per 24 hours, and extracted nucleic acids were interrogated for the presence of SARS-CoV-2 by quantitative reverse-transcriptase PCR. Dates of positive detection were overlayed with dates of confirmed cases in the student population to determine assay sensitivity. SARS-CoV-2 was detected numerous times and was often, but not always, followed by cases of COVID-19. Positive student cases were preceded by detection of SARS-CoV-2 in wastewater by up to 48 hours at each detection. The positive predictive value of wastewater detection for student COVID-19 cases was 0.8105, and the negative predictive value was 0.991. Wastewater screening has the potential to serve as a tool for community-level SARS-CoV-2 surveillance, and is particularly powerful as a negative predictor of disease activity.