Defining the methodological approach for wastewater-based epidemiological studies-Surveillance of SARS-CoV-2

Abstract

Since COVID-19 outbreak, wastewater-based epidemiology (WBE) studies as surveillance system is becoming an emerging interest due to its functional advantage as a tool for early warning signal and to catalyze effective disease management strategies based on the community diagnosis. An attempt was made in this study to define and establish a methodological approach for conducting WBE studies in the framework of identifying/selection of surveillance sites, standardizing sampling policy, designing sampling protocols to improve sensitivity, adopting safety protocol, and interpreting the data. Data from hourly sampling indicated a peak in the viral RNA during the morning hours (6-9 am) when the all the domestic activities are maximum. The daily sampling and processing revealed the dynamic nature of infection spread among the population. The two sampling methods viz. grab, and composite showed a good correlation. Overall, this study establishes a structured protocol for performing WBE studies that could provide useful insights on the spread of the pandemic at a given point of time. Moreover, this framework could be extrapolated to monitor several other clinically relevant diseases. Following these guidelines, it is possible to achieve measurable and reliable SARS-CoV-2 RNA concentrations in wastewater infrastructure and therefore, provides a methodological basis for the establishment of a national surveillance system.

Keywords: Composite sample; Domestic sewage treatment plants (STP); Grab sample; Sampling protocol; Urban area.

Graphical abstract

Fig. 1

Sampling point selected for daily and hourly monitoring at the inlet of the STP in Nacharam, Hyderabad.

Fig. 2

(a) C${}_{\mathrm{T}}$ values of E gene, N gene, and ORF1ab; (b) RNA copies calculated based on linear fit equation of E-gene of samples collected hourly from selected point (All values represent, $\overline{X}$+SD).

Fig. 3

(a) C${}_{\mathrm{T}}$ values of E gene, N gene, and ORF1ab; (b) RNA copies of hourly samples calculated based on linear fit equation of E-gene (All values represent, $\overline{X}$+SD).

Fig. 4

(a) C${}_{\mathrm{T}}$ values of E gene, N gene, and ORF1ab and RNA copies of hourly, daily average and composite samples (All values represent, $\overline{X}$+SD).