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How wastewater testing is helping to decode public health

Wastewater surveillance and monitoring are growing in popularity as a testing tool for public health monitoring. But how does it work?
How wastewater testing is helping to decode public health
Posted at 8:04 PM, Oct 21, 2023

With every rinse of a sink and flush of a toilet, public health is becoming easier to track thanks to a growing practice known as wastewater monitoring or wastewater surveillance.

"This is an information stream that is continually flowing every day," said Aparna Keshaviah, the director of wastewater research at Mathematica.

It's the collection of samples of wastewater from sewage treatment facilities that allows health experts to monitor for illnesses and outbreaks in a community.

"Wastewater surveillance isn't new. It's been used since the 1960s for polio surveillance," Dr. Amy Kirby, leader of the National Wastewater Surveillance System, said. "We've talked about it for other pathogens since then, other diseases, but it really hasn't made sense to stand up this system nationally for these other diseases. But in the face of a pandemic that was causing so many illnesses and so many deaths and moving so quickly, the calculation behind that, you know, risk benefit really changed, and it became worth it to build this system."

The National Wastewater Surveillance System is operated by the Centers for Disease Control and Prevention.

Kirby says the system, launched in September 2020, was created with the purpose of expanding the U.S. ability to track the virus that causes COVID-19, SARS-CoV-2, across the country.

"So currently we're testing at about 1,600 sites, which is amazing. We capture over 40% of the US population in those 1,600 sites, but there are 16,000 permitted wastewater treatment plants in the U.S.," Kirby said.

So, how exactly does this practice work?

"You have a sampler that takes a small-like sip of the wastewater as it comes through the pipes into the treatment plant over 24 hours. So, it's sampling like every 20 minutes," Kirby said. "So, we take that composite 24-hour sample that's then shipped to a testing laboratory. So, it's usually about 100 mils. So, you know, coffee cup-ish. And then they take that sample, and they concentrate all of the viruses out of it."

This practice is now being expanded to test for other public health makers.

"It's very far reaching beyond, you know, pathogenic viruses and bacteria. It includes illicit drugs and substance use. You can monitor for markers of chronic diseases. You can monitor for stress," Keshaviah said.

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Mathematica, a research and data analytics consultancy, has been coordinating with municipalities and community partners to scale wastewater testing and create decision support tools.

As a leading expert in wastewater-based epidemiology, Keshaviah says the testing possibilities are endless but will take some time to expand.

"The testing methods will need to be refined for each. Some are at, you know, earlier stages of development than others. But we could think about, you know, monitoring people's localized exposure to pollution or, you know, climate-related environmental exposures, which would be a huge advancement in the field of environmental monitoring," Keshaviah said.

She says part of what makes the practice so appealing is that it yields non-identifying data, meaning folk's privacy is generally protected.

"It is collecting information on health markers in mass, meaning you are not isolating a single household; you're looking at hundreds, thousands, up to a million people represented in a single sample, Keshaviah said.

While the risk of privacy invasion isn't high, the U.S. Government Accountability Office says they do have some concerns, saying in part, "Wastewater surveillance raises privacy and ethical concerns because wastewater contains not only a pathogen's genetic data that allows public health officials to identify the pathogen but also human genetic data that could potentially be misused." The U.S. Government Accountability Office also notes that there is a risk that communities could be stigmatized based on the findings of tests.

Currently, wastewater testing capabilities vary depending on where you are in the U.S. Long-term, Keshaviah says improving wastewater infrastructure and solidifying a reporting platform will be beneficial for everyone.

"This is a real opportunity now for communities to kind of advance and upgrade that infrastructure because it can provide information on so many things," Keshaviah said. "Data needs to be expanded. It needs to be connected, and it needs to be reported in a way that facilitates action not just across the U.S. but globally as well, because the next health threat may not emerge in the U.S., just like with COVID."

So for the sake of public health, it looks like our waste should not be wasted.

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