Every day, we could be flushing critical coronavirus data down the toilet. According to scientists, the clue to when society will reopen seems to be in the sewer.
By Sofia Popov
More and more of us have grown downcast amidst the worsening economy and need to confine. Society is at somewhat of a standstill, and we’re still in the dark in many ways, figuring out what happens next, what this all means, and what we can do about it. Fortunately, scientists are shedding some light. Turns out, our stools could give us the signals we need: finally, we may find out when social distancing measures can be relaxed, and social norms return.
Wastewater analyses have been used by teams of researchers, from Stanford to Paris, in order to track how SARS-CoV-2 – the virus that causes COVID-19 – spreads. Initial studies show that monitoring sewage, otherwise known as “wastewater-based-epidemiology,” can be used to tell us, not only how far a virus has spread in a given community, but also when it’s actually gone away.
With wastewater, it’s possible to rapidly get an overview of an entire population. This can empower us with data that is literally like testing every single person in a community, and taking an average of that. Experts argue that detecting the virus in sewage can mirror the timing and scale of an outbreak in ways that in-person testing cannot – whilst also doing so at a quicker and cheaper manner. Together, this information can hold critical for informing and validating public health decisions. It can potentially fill the gaps presented in this pandemic thus far: understanding the true scale of COVID-19.
The Sh*t Show
Historically, wastewater has successfully been used as an early warning system, helping catch norovirus, Hepatitis A and other diseases around the world for decades. For instance, a 2013 polio epidemic¹ in Israel was picked up by sewage – before any clinics had reported cases. This early alert gave the government time to contain the virus.
Now, as cities start loosening their stay-at-home orders over the coming weeks and months, some suggest that monitoring sewage could offer early warnings if it suddenly makes a comeback.
As cities start loosening their stay-at-home orders over the coming weeks and months, some suggest that monitoring sewage could offer early warnings if it suddenly makes a comeback.
Sewage monitoring is currently already in effect in Australia, where it’s applied for better understanding patterns of drug use, such as cocaine – something that would otherwise be difficult to test and track. Similarly, France has used sewage samples to confirm changing concentrations of SARS-CoV-2 in Paris². Meanwhile, in the Netherlands, this method helped a research team detect the virus in a city’s sewage before any local COVID-19 cases had been reported by officials³.
Everything Ends up in the Sewer
Researchers from MIT and Harvard carefully looked at virus particles in sewage samples at a wastewater treatment plant over the course of a week in March⁴. Their findings, released this month, revealed a much higher number of infected people in the area than what clinical confirmations had indicated.
The sewage samples revealed that, compared to the 446 reported cases, their numbers went from a conservative estimate of 2300, all the way up to 115,000 people that were actually infected.
Notably, the sewage samples revealed that, compared to the 446 reported cases, their numbers went from a conservative estimate of 2300, all the way up to 115,000 people that were actually infected and potentially shedding the virus to others during that period.
Of course, there are still quite a few questions the researchers need to figure out: how much virus can we each shed for each toilet trip? How can we account for other factors that may dilute the sample?
Nevertheless, it seems that routine wastewater monitoring could help us be more proactive, and help prevent future outbreaks.
Progress in technology has made sewage testing much more affordable and quicker. Now, with SARS-CoV-2, analyzing sewage is aiding understanding for both officials and scientists, offering a clear picture of the true level of outbreak, as well as how well it’s being contained, says Charles Gerba, a professor of microbiology at the University of Arizona.
Till now, this tool has been largely untapped. Starting now, and proceeding into the future, fine-tuning these alerts could help inform our cities on any incoming viral threats – and help us be better prepared if something like COVID-19 returns for round two.
- Brouwer, Andrew & Eisenberg, Joseph & Pomeroy, Connor & Shulman, Lester & Manor, Yossi & Grotto, Itamar & Koopman, James & Eisenberg, Marisa. (2018). Epidemiology of the silent polio outbreak in Rahat, Israel, based on modeling of environmental surveillance data. Proceedings of the National Academy of Sciences. 115. 201808798. 10.1073/pnas.1808798115
- Wurtzer, Sebastien & marechal, vincent & Mouchel, Jean-Marie & Moulin, Laurent. (2020). Time course quantitative detection of SARS-CoV-2 in Parisian wastewaters correlates with COVID-19 confirmed cases. 10.1101/2020.04.12.20062679.
- Medema, Gertjan & Heijnen, Leo & Elsinga, Goffe & Italiaander, Ronald & Brouwer, Anke. (2020). Presence of SARS-Coronavirus-2 in sewage. 10.1101/2020.03.29.20045880.
- Wu, Fuqing & Xiao, Amy & Zhang, Jianbo & Gu, Xiaoqiong & Lee, Wei & Kauffman, Kathryn & Hanage, William & Matus, Mariana & Ghaeli, Newsha & Endo, Noriko & Duvallet, Claire & Moniz, Katya & Erickson, Timothy & Chai, Peter & Thompson, Janelle & Alm, Eric. (2020). SARS-CoV-2 titers in wastewater are higher than expected from clinically confirmed cases. 10.1101/2020.04.05.20051540.