Coordination of SARS-CoV-2 wastewater and clinical testing of university students demonstrates the importance of sampling duration and collection time

Abstract

Wastewater surveillance has been a useful tool complementing clinical testing during the COVID-19 pandemic. However, transitioning surveillance approaches to small populations, such as dormitories and assisted living facilities poses challenges including difficulties with sample collection and processing. Recently, the need for reliable and timely data has coincided with the need for precise local forecasting of the trajectory of COVID-19. This study compared wastewater and clinical data from the University of Delaware (Fall 2020 and Spring 2021 semesters), and evaluated wastewater collection practices for enhanced virus detection sensitivity. Fecal shedding of SARS-CoV-2 is known to occur in infected individuals. However, shedding concentrations and duration has been shown to vary. Therefore, three shedding periods (14, 21, and 30 days) were presumed and included for analysis of wastewater data. SARS-CoV-2 levels detected in wastewater correlated with clinical virus detection when a positive clinical test result was preceded by fecal shedding of 21 days (p< 0.05) and 30 days (p < 0.05), but not with new cases (p = 0.09) or 14 days of shedding (p = 0.17). Discretely collected wastewater samples were compared with 24-hour composite samples collected at the same site. The discrete samples (n = 99) were composited examining the influence of sampling duration and time of day on SARS-CoV-2 detection. SARS-CoV-2 detection varied among dormitory complexes and sampling durations of 3-hour, 12-hour, and 24-hour (controls). Collection times frequently showing high detection values were between the hours of 03:00 to 05:00 and 23:00 to 08:00. In each of these times of day 33% of samples (3/9) were significantly higher (p < 0.05) than the control sample. The remainder (6/9) of the collection times (3-hour and 12-hour) were not different (p > 0.05) from the control. This study provides additional framework for continued methodology development for microbiological wastewater surveillance as the COVID-19 pandemic progresses and in preparation for future epidemiological efforts.

Keywords: COVID-19; Method development; SARS-CoV-2; Virus recovery; Wastewater-based epidemiology.

Graphical abstract

Fig. 1

Wastewater production for dormitory complexes A (suite-style, light solid), B (suite-style, dark solid), C (apartment-style, dark striped), and D (traditional style, light striped) data by month during 2020-2021 academic year. Data are presented as the total wastewater produced for each complex throughout the month (gallons).

Fig. 2

Dormitory complex A, SARS-CoV-2 clinical (A) and SARS-CoV-2 wastewater surveillance (B) data during the 2020-2021 academic year. Vertical bars show weekly total of positive clinical cases (left vertical axis). Shaded areas show clinical cases with potential shedding including both new and recovering case patients (right vertical axis): dark (14-days); medium (21-days); and light (30-days) of SARS-CoV-2 fecal shedding after an initial positive clinical test. Wastewater data are presented as SARS-CoV-2 viral copies per liter of wastewater.

Fig. 3

Dormitory complex B, SARS-CoV-2 clinical (A) and SARS-CoV-2 wastewater surveillance (B) data during the 2020-2021 academic year. Vertical bars show weekly total of positive clinical cases (left vertical axis). Shaded areas show clinical cases with potential shedding including both new and recovering case patients (right vertical axis): dark (14-days); medium (21-days); and light (30-days) of SARS-CoV-2 fecal shedding after an initial positive clinical test. Wastewater data are presented as SARS-CoV-2 viral copies per liter of wastewater.

Fig. 4

SARS-CoV-2 wastewater surveillance data for dormitory complex C, during the 2020-2021 academic year.

Fig. 5

Levels of SARS-CoV-2 detected in wastewater from 3 dormitory complexes (A, C, and D), collected in 3-, 12-, and 24-hour composite samples. Detection levels displayed are dCT values, obtained from RT-qPCR performed in which greater dCT values represent greater levels of virus, SARS-CoV-2. Twenty-four-hour composite samples were used as controls. Shading represents significance (p < 0.05) of detection levels: light gray (no significant difference), dark gray (significantly higher), and white (significantly lower). Outlines represent the three collection dates: red (left), green (middle), and blue (right) in each time period.