As the highly contagious omicron variant continues to drive up coronavirus infections and overwhelm hospitals, CDC's National Wastewater Surveillance System (NWSS) is using sewage to track the spread of the coronavirus.

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Tracking Covid-19 surges with wastewater

According to CDC, people infected with the coronavirus will expel traces of the virus in their stool. As a result, virus levels in a community's wastewater provide a reliable indicator of how much it is spreading within a certain community.

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In fact, this type of testing can detect the presence of the virus if just one individual out of 100,000 is infected in a given area, CNN reports.

Moreover, wastewater surveillance provides the earliest warning of an impending Covid-19 surge because it does not depend on people testing after they realize they are sick. Wastewater testing can detect the virus in asymptomatic individuals who may not take a test at all.

"As long as people are using a toilet that's connected to a sewer, we can get information on those cases in that community," said Amy Kirby, a CDC microbiologist who leads the NWSS project. She added, "Wastewater surveillance is a really powerful tool, and we're seeing really a good example of that with omicron. It's not just an early warning sign, but it's also helpful to monitor the full trajectory of a surge."

As a result, wastewater surveillance has helped guide the local pandemic response in some communities. Public health officials have used it to target their mitigation efforts into areas where the virus is surging. Hospitals have also used it to make critical decisions about which treatments to administer to their patients, the New York Times reports.

However, these efforts are confined to communities with reliable data that is easily accessible, leading some experts to argue that the United States needs to take immediate action to expand and coordinate widespread wastewater surveillance efforts.

Currently, there is no centralized public dashboard that displays all of the nation's wastewater data. In comparison, the Netherlands has a national wastewater surveillance system that is updated daily and includes almost all of its residents.

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"I absolutely believe the U.S. is behind," said Mariana Matus, CEO and co-founder of Biobot Analytics, a company that is currently conducting wastewater surveillance for the coronavirus in 183 communities across 25 states, according to the Times.

Creating a reliable wastewater surveillance system

Throughout the pandemic, scientists, health officials, and biotech companies have been developing wastewater surveillance systems designed to detect new variants, track the virus' spread, and issue a warning for coming surges.

In September 2020, CDC launched NWSS to coordinate and build the nation's capacity to track the presence of SARS-CoV-2 in wastewater samples collected across the United States. CDC's NWSS works with state, tribal, territorial, and local health departments to track SARS-CoV-2 levels in wastewater so communities can rapidly detect and control outbreaks of Covid-19. This can effectively transform small, local efforts into a reliable, sustainable national surveillance system.

In the coming weeks, CDC—which is now funding sewage surveillance efforts across 43 states, cities, and territories—will start adding wastewater surveillance data from more than 500 sites to its online "Covid Data Tracker," the Times reports.

However, the success of these systems depends largely on officials' willingness to implement them, as well as how quickly CDC can obtain results. Currently, among the 43 jurisdictions funded by CDC, only 13 have "fully implemented" their systems and are routinely submitting data to the agency, according to Kirby.

Some communities collect wastewater only about once a week, and there is typically a delay of at least a few days before the results become available. This makes it difficult to track a fast-moving variant—such as omicron—in real time, the Times reports.

"Our turnaround time is never quick enough," Kirby acknowledged.

Still, Kirby said wastewater surveillance will outlast the Covid-19 pandemic. In fact, CDC plans to expand the number of pathogens it tracks on the dashboard to include influenza, Candida auris, and foodborne illnesses such as E. coli and salmonella. (Goodman, CNN, 2/3; CDC's National Wastewater Surveillance System, accessed 2/4; Anthes/Imbler, New York Times, 1/19)