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WEF update explores virus detection methods, infectivity through wastewater

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As wastewater increasingly becomes part of the mainstream conversation during the COVID-19 pandemic as a tool to measure the spread of the virus, the Water Environment Federation (WEF) is reminding water professionals that these testing methods do not assess virus viability or infectivity.

After providing an initial primer on COVID-19 in February, the WEF released an expansion document this week to highlight the unlikely survival of infective COVID-19 virus in feces and wastewater systems. In other words, exposure to wastewater is not a significant transmission route for the COVID-19 virus (technically named SARS-CoV-2), WEF officials wrote in their Update and Expansion on The Water Professional’s Guide to COVID-19.

While much is still unknown about COVID-19 virus shedding and transmission, the CDC and WHO state that current evidence does not support that the COVID-19 virus is transmitted via wastewater.

The WEF’s Waterborne Infectious Disease Outbreak Control (WIDOC) working group has been tasked with highlighting the latest scientific findings, as well as topics not previously addressed in the initial field guide posting.

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“No coronavirus-specific protections are recommended for workers working in wastewater treatment and collection systems,” the WEF update states. “However, as data emerges almost daily with regard to this virus, heightened vigilance in compliance with existing personal protective procedures is appropriate to control exposure,” the authors add. 

Testing Methods
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(Click to enlarge) COVID-19 virus potential detection methods for clinical and environmental samples. Graphic credit: WEF

In terms of testing underway to assess the spread of COVID-19, some tests can determine whether the virus can infect cells, while others just look for nucleic acids, also called RNA or RNA fragments, according to the WEF.

“But viruses need much more than just their RNA to successfully infect cells, so detecting RNA is a little bit like detecting an antibody — it tells you that the virus was once there, but not whether it is still there and is infectious now,” states the WEF update, which offers a deep dive into virus structure and function.

In examining environmental virology and the various methods used to detect viruses, the WEF states that the advent of cell culture assays was a “major catalyst for improving our understanding of waterborne viruses and their transmission routes.” In cell culture assays, the posting informs, a water or wastewater sample is added to a prepared population of suitable host cells. This was the detection used for poliovirus surveillance in wastewater in the 1940s.

“Cell culture assays are expensive, time-consuming, susceptible to contamination, and require specialized equipment and reagents,” wrote researchers in the WEF update, indicating that researchers often opt for other detection methods for several reasons.

The WEF also looks at a detection method that has become more popular in the Netherlands, Australia and the U.S. during COVID-19. Known as reverse transcriptase-PCR (RT-PCR), the method is a type of nucleic acid-based test (PCR) used to detect the presence of ribonucleic acid (RNA) viruses.

The WEF update document directs readers to three new studies that investigated the use of wastewater-based epidemiology approaches to support public health surveillance for COVID-19 infections in communities. One publication is a pre-proof from Australia by Ahmed et al. (2020), while the other two are not yet peer-reviewed: Medema et al. (2020) from KWR Watercycle Research Institute in the Netherlands and Wu et al. (2020) from Biobot in Massachusetts.

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