Making waves: Defining the lead time of wastewater-based epidemiology for COVID-19

Water Res. 2021 Sep 1;202:117433. doi: 10.1016/j.watres.2021.117433. Epub 2021 Jul 15.


Individuals infected with SARS-CoV-2, the virus that causes COVID-19, may shed the virus in stool before developing symptoms, suggesting that measurements of SARS-CoV-2 concentrations in wastewater could be a "leading indicator" of COVID-19 prevalence. Multiple studies have corroborated the leading indicator concept by showing that the correlation between wastewater measurements and COVID-19 case counts is maximized when case counts are lagged. However, the meaning of "leading indicator" will depend on the specific application of wastewater-based epidemiology, and the correlation analysis is not relevant for all applications. In fact, the quantification of a leading indicator will depend on epidemiological, biological, and health systems factors. Thus, there is no single "lead time" for wastewater-based COVID-19 monitoring. To illustrate this complexity, we enumerate three different applications of wastewater-based epidemiology for COVID-19: a qualitative "early warning" system; an independent, quantitative estimate of disease prevalence; and a quantitative alert of bursts of disease incidence. The leading indicator concept has different definitions and utility in each application.

Keywords: COVID-19; SARS-CoV-2; Surveillance; Wastewater-based epidemiology.

Publication types

  • Review

MeSH terms

  • COVID-19*
  • Humans
  • Lead
  • SARS-CoV-2
  • Waste Water
  • Wastewater-Based Epidemiological Monitoring*


  • Waste Water
  • Lead