An international group of environmental experts assessed the potential impact of SARS-CoV-2 in wastewater on public health.
Public health strategies to control the COVID-19 pandemic are aimed at reducing the spread of the highly contagious SARS-CoV-2 virus. The main mode of transmission of the virus is by close personal contact through respiratory droplets, aerosols, and mutual surface contact – but there may be additional sources of spread.
During the SARS-CoV-1 outbreak in 2003, evidence from a cluster of cases in an apartment block suggested that the virus could spread via contaminated wastewater, either by respiration of aerosols created by flushing toilets or via faulty plumbing systems. SARS-CoV-2 is also found in feces samples from infected individuals and there is some concern that the virus could spread indirectly through wastewater systems. An international group of environmental experts evaluated the current evidence oncoronavirus in wastewater and considered the public health risks and areas for future research. Their review is published in Nature Sustainability.
Coronavirus in wastewater may be an indirect mode of transmission
The researchers evaluated a wide range of evidence related to SARS-CoV-2 in wastewater including; the possible sources of the virus; detection methods, infectivity and survival of the virus in wastewater; potential for dissemination in sewer systems; and virus dispersion via crop irrigation with treated wastewater, or in surface water and groundwater. They also reviewed recent surveillance of COVID-19 outbreaks via wastewater monitoring and considered the efficacy of conventional and advanced water treatment methods to reduce viral dissemination.
The evidence so far suggests that infective SARS-CoV-2 virus particles can be detected in wastewater and could potentially be disseminated through sewage systems leaking into natural watercourses, or by inadequately treated wastewater used to irrigate crops or fill recreational water systems such as lakes and rivers. The researchers point out that 3.5 billion people worldwide use unsafe sanitation and this allows the transmission of many viral diseases including SARS-CoV-2. This could be a particularly important factor in the spread of the COVID-19 pandemic in low-income countries.
Even in developed nations, conventional wastewater treatment practices may not be sufficient to remove or inactivate viruses such as SARS-CoV-2 and this requires urgent further investigation. Putting in place more advanced wastewater treatments such as low-pressure or high-pressure membrane filtration technologies may provide a complete barrier to SARS-CoV-2 and other viruses.
Monitoring of SARS-CoV-2 levels in sewage systems has recently been suggested as a tool to help identify community outbreaks of COVID-19, in addition to individual COVID-19 testing programs. Sewage monitoring could give an early warning signal of an outbreak, as changes in SARS-CoV-2 concentrations in wastewater can precede changes in confirmed COVID-19 case numbers by several days. This would allow the early adoption of appropriate public health restrictions. It may be particularly helpful in monitoring communities with a previous COVID-19 outbreak.
Urgent need for further investigation of coronavirus in wastewater
The experts concluded that there is already sufficient evidence to be concerned about how coronavirus in wastewater affects public health risk. “Can wastewater contain enough coronaviruses to infect people? The simple truth is that we do not know enough and that needs to be rectified as soon as possible” said Dr Edo Bar-Zeev of the Ben Gurion University Zuckerberg Institute, the lead author of the study.
The authors recommend urgent investigations to determine the level of risk in different country populations including extensive research into the frequency of detecting SARS-CoV-2 in wastewater and identifying and mitigating risks of SARS-CoV-2 transmission via waterborne pathways. They also recommend that wastewater treatment plants update their treatment protocols to ensure successful removal of viruses. These approaches will not only help to contain the COVID-19 pandemic, but also future viral disease outbreaks.
Written by Julie McShane, MA MB BS
1. Bogler A, Packman A, Furman A, et al. Rethinking wastewater risks and monitoring in light of the COVID-19 pandemic. Nature Sustainability (Published online, 19 Aug, 2020).
2. American Associates, Ben Gurion University of the Negev. Press releases, 24 Aug 2020. Could COVID-19 in wastewater be infectious? https://www.eurekalert.org/pub_releases/2020-08/aabu-cci082320.php
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