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We may have a surprising new ally in our bid to contain the Covid-19 outbreak: its sewage.
The Australian government recently announced that the wastewater will be tested for SARS-CoV-2, the coronavirus that causes Covid-19. Federal health minister Greg Hunt explained that this will be a key part of the monitoring program that must be implemented to protect against future local outbreaks of the virus.
Researchers in the Netherlands, France, the United States and Australia have been testing wastewater for SARS-CoV-2 for more than a month, and have generally reported that the rise and fall of their results reflect local infection rates. with Covid officially reported. -19.
This suggests that wastewater can be used to monitor the future spread of the virus. And with many infections considered to be symptom-free, this means that we can potentially detect cases that other monitoring programs could evade.
SARS-CoV-2 tests in sewage do not detect the virus itself, but only a very small fragment – about 0.1% – of the virus’ genetic material, called RNA. This means that you cannot determine if the water contains infectious virus particles or just a few pieces of inactivated or decomposed virus leftover RNA.
This type of waste tracking is not new. It has already been used in Australia to track viruses such as norovirus. And since 2017, sewer tests have been used to uncover evidence of illicit drug use at the population level. Drug test wastewater has helped police and other authorities discover what drugs are used in particular cities, and even locate illicit drug labs.
The newest aspect is the proposal to use wastewater monitoring in the context of a major pandemic, and potentially rely on the data to inform some high-risk decisions. This introduces a heavy burden of responsibility to ensure that data is collected by reliable means, with well-understood rates of false results, both positive and negative.
If the main decisions are based on the measured concentrations, it will be essential to understand all the factors behind these measurements.
What is the protocol?
While technically possible, sewage testing of individual properties is unlikely to be cost-effective. But it could be used to collect wastewater samples from large buildings, hospitals, or even ships or planes.
It will be important to understand how we would respond to positive results for SARS-CoV-2. Locking a building or cruise ship may require isolation for everyone involved. Alternatively, a positive result could be used as a trigger for individual testing of those individuals who may have contributed to the positive wastewater sample. In any case, the impacts on people will be enough to guarantee high reliability for wastewater tests.
Meanwhile, how safe can we be about wastewater that is negative for SARS-CoV-2? Do we adequately understand the probability of losing what might have been a positive result? Would liability be imposed on test authorities, governments or others in the event of false negatives leading to missed opportunities for virus containment?
We will also need to understand the trends that can be observed in terms of increasing and decreasing concentrations of SARS-CoV-2 in wastewater. Although we can assume that these accurately reflect changing infection patterns, other factors such as rainfall and sampling variability could significantly influence the measured concentrations.
Of course, direct clinical testing of patients is also subject to many types of errors, and there are protocols for how we respond. But the wastewater tests would likely have higher degrees of uncertainty and more people directly affected by the responses. Therefore, the problem is much less direct than it might seem at first reflection.
Right of discharge
If coronavirus testing is to be used to dictate specific actions or responses from public health officials under emergency orders, it raises questions that have yet to be addressed in Australian drug testing.
A testing regimen that provides information on the scale that would be most useful to public health would create human rights challenges. The human right to water is recognized by international law and includes the right to safe and accessible sanitation. If wastewater testing is used to support sanctions in the form of blockages, this can erode our basic right of access to sanitation.
This type of testing also poses challenges for public water authorities, who must comply with the Principles of Information Privacy.
We may also wonder where our own “rights” to our waste end. In Australia, household trash remains the legal property of the homeowner while it is on their private property, but it belongs to the garbage collection agency, usually a local government, once collected. Is this an appropriate model for body waste?
Australia’s legal frameworks around wastewater collection, treatment and management have struggled to keep up with developments in sewerage mining, stormwater reuse and water recycling. It may seem strange to reflect on the ethics of what people flush down the toilet. But given the personal details that sewage can reveal, from disease and pollutants to drug and alcohol use, we need a national framework to ensure that technology is not left unchecked.
Anna Kosovac, researcher in International Urban Policy, University of Melbourne. Erin O’Donnell, Early Career Scholar, Resource Center, Energy Law and Environment, University of Melbourne. Stuart Khan, professor of civil and environmental engineering, UNSW.
This article first appeared in The Conversation.
