The Value of Wastewater Surveillance to Support COVID-19 Response in a Community with Large-scale Asymptomatic Testing

SARS CoV-2 Wastewater Testing - State of the Science
Oral Presentation

Prepared by H. Safford
UC Davis, 1317 Chestnut Lane, Davis, California, 95616, United States

Contact Information:; 415-419-4106


Wastewater-based epidemiology (WBE) has become widely recognized as a useful complement to clinical testing for monitoring and informing response to the spread of COVID-19. Key advantages of WBE relative to large-scale testing include that the former (1) is a less resource-intensive way to gather information on large numbers of individuals, (2) provides data on entire populations rather than just the subset of individuals who come in for clinical testing, and (3) can serve as an early-warning system, given that fecal shedding of SARS-CoV-2 typically precedes symptom onset.

Viable public-health implications of WBE depend on the scale at which it is carried out. Samples collected from the outflows of high-priority buildings (such as skilled nursing facilities or college dorms) can trigger direct, targeted responses. Sewershed samples can help officials compare trends across neighborhoods and determine how best to allocate public-health resources such as testing, contact tracing and vaccination outreach. Finally, samples collected from influent to wastewater treatment plants (WWTPs) provide information on overall virus trends within a population. This information can reinforce confidence in trends apparent from clinical data—or suggest when clinical testing may be missing key population segments. Data collected from sewershed and WWTP influent samples can also be incorporated into public-education and outreach campaigns.

This presentation focuses on a program applying WBE at all three of these scales in a single community: the Healthy Davis Together (HDT) program in Davis, CA. Since October of 2020, HDT has offered free asymptomatic COVID-19 testing for anyone living or working in Davis. HDT has also been performing rapid quantification of SARS-CoV-2 in—and metagenomic sequencing of—wastewater samples regularly collected at the building/neighborhood, sub-regional, and city-wide scales. This presentation will consider how the value of WBE in a community where asymptomatic testing is widely available and accessible differs from one in which it is not. It will also explore the importance of thoughtful presentation of wastewater data and appropriate treatment of non-detects, as well as frameworks for action based on WBE results.