WB Epidemiology

By Ian Pepper, Walter Betancourt, Charles P. Gerba, University of Arizona WEST Center

Wastewater Based Epidemiology (WBE) is a rapidly expanding new discipline formerly known as Sewage Surveillance. The concept behind WBE is that the concentration of specific microorganisms and/or chemicals in sewage is a reflection of the total inputs of these constituents from a given community. For SARS-CoV-2 and wastewater treatment plants, the concentration of Coronavirus in the sewage is a reflection of the total virus load resulting from the members of the community served by the plant. Critically important is the fact that the total virus load reflects viruses shed by infected individuals with symptoms, as well as infected individuals who are asymptomatic. Thus, assaying the sewage for the virus monitors a given community with one test, and answers the question: “Is the virus currently present in the community?” Answering this question during the reopening of the UA Campus was critical for the prevention of the spread of the virus since WBE is a leading indicator (1 week in advance of symptoms in individuals; Peccia et al., 2020). The sensitivity of detection of WBE is one infected individual in 10,000. This document describes a case study of WBE as a preventative tool to monitor the UA community for Coronavirus in near real-time, as students re-entered campus in the fall of 2020. The major WBE activity was monitoring sewage from UA communities located within dormitories.

collecting ww at dorms

On August 17, students from the University of Arizona started returning to Campus for in-person classes for the Fall Semester. At this time, the WEST Center began WBE as part of the Campus Re-entry Plan (Information Box 1). Wastewater samples from manholes from several student dormitories tested negative for COVID-19 on August 18 and 20. Classes began on August 24, and routine monitoring of 15 student dormitories was initiated. Critical to the plan was the decision to sample sewers from single dormitories so that wastewater was collected from a defined community of students.

WW teams

On August 25, wastewater from a specific dormitory, here identified as Dorm A, produced a positive test for COVID-19. This resulted in an emergency meeting of the Campus Re-entry Task Force and two decisions were made:

  1. To take more wastewater samples (August 26)
  2. To clinically test all residents for COVID-19 (August 26)

Results of the antigen testing identified two students that were infected with Coronavirus, both of whom were asymptomatic (no symptoms). These two students were removed from Dorm A and put into an Isolation Dorm. The following day August 27, wastewater samples from Dorm A were again collected, and upon PCR analysis, were found to be negative for the virus. Thus, once the source of the virus (the two infected students) was removed from the dorm, WBE correctly provided the negative wastewater result. The fact that the two infected students were asymptomatic means that without WBE identification, these students would have been free to interact with other students for several additional days prior to symptom development, potentially increasing exponential spread of the virus.

Overall, WBE helped avert an outbreak of COVID-19 on Campus, and the news resulted in a frenzy of media activity, including broadcasts on CNN, NPR, ABC, NBC, and CBS; dozens of newspaper reports (Information Box 2); and articles in “The Atlantic” and “Politico.” Since the report of this Case Study was announced, numerous universities in the U.S. and abroad are implementing WBE for monitoring student dorms. As of the 8th week of the semester, the case count here at the University of Arizona is minimal, and in-person classes are still proceeding. Thus, WBE has helped UA remain open, whereas multiple universities in the U.S. have had to close up, due to COVID-19.

media reports

Reference:  Peccia, J., Zulli, A., Brackney, D.E., Grubaugh, N.D., Kaplan, E.H., Casanovas-Massana, A., Ko, A.I., Malik, A.A., Wang, D., Wang, M., Weinberger, D.M., Omer, S.B. 2020. SARS-CoV-2 RNA concentrations in primary municipal sewage sludge as a leading indicator of COVID-19 outbreak dynamics. https://doi.org/10.1101/2020.05.19.20105999