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Estimating virus occurrence using Bayesian modeling in multiple drinking water systems of the United States
Citation:
Varughese, E., N. Brinkman, E. Anneken, J. Cashdollar, Shay Fout, E. Furlong, D. Kolpin, S. Glassmeyer, AND S. Keely. Estimating virus occurrence using Bayesian modeling in multiple drinking water systems of the United States. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 619620:1330-1339, (2018).
Impact/Purpose:
This manuscript is part of a series of manuscripts associated with the overview paper titled "Nationwide reconnaissance study of contaminants of emerging concern in source and treated drinking water" by Susan Glassmeyer et al. Although associated with a series of papers, this manuscript was written as a standalone body of work and only references the overview paper for additional details on the sampling sites. This particular study is the first to incorporate a unique multi-step approach to examine the occurrence of multiple human-pathogenic viruses in source (natural) waters and treated waters from various sites across the nation. Specifically, we looked at 5 different types of viruses: adenovirus (AdV), enterovirus (EV), norovirus GI (NoV GI), norovirus GII (NoV GII), and polyomavirus (PyV). PCR count data for each virus was integrated with other parameters such as recovery efficiency and inhibition limitations for the different water types into a Bayesian model to estimate viral loads in source and treated waters. Employing multiple parameters will not only allow us to achieve a more accurate understanding of viral quantities from our water systems, but will increase our knowledge of tracking and removal of pathogenic human viruses.
Description:
Drinking water treatment plants rely on purification of contaminated source waters to provide communities with potable water. One group of possible contaminants are enteric viruses. Measurement of viral quantities in environmental water systems are often performed using polymerase chain reaction (PCR) or quantitative PCR (qPCR). However, true values may be underestimated due to challenges involved in a multi-step viral concentration process and due to PCR inhibition. In this study, water samples were concentrated from 25 drinking water treatment plants (DWTPs) across the US to study the occurrence of enteric viruses in source water and removal after treatment. The five different types of viruses studied were adenovirus, norovirus GI, norovirus GII, enterovirus, and polyomavirus. Quantitative PCR was performed on all samples to determine presence or absence of these viruses in each sample. Ten DWTPs showed presence of one or more viruses in source water, with four DWTPs having treated drinking water testing positive. Furthermore, PCR inhibition was assessed for each sample using an exogenous amplification control, which indicated that all of the DWTP samples, including source and treated water samples, had some level of inhibition, confirming that inhibition plays an important role in PCR-based assessments of environmental samples. PCR inhibition measurements, viral recovery, and other assessments were incorporated into a Bayesian model to more accurately determine viral load in both source and treated water. Results of the Bayesian model indicated that viruses are present in source water and treated water. By using a Bayesian framework that incorporates inhibition, as well as many other parameters that affect viral detection, this study offers an approach for more accurately estimating the occurrence of viral pathogens in environmental waters.
