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May 29, 2020

Scientists are eyeing a new way to predict Covid-19 outbreaks. (It involves your sewage.)

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    As states consider easing social distancing guidelines, infectious disease experts are exploring whether wastewater testing can be used to detect potential Covid-19 outbreaks—before they occur.

    Your top resources for Covid-19 response and resilience

    Why wastewater testing?

    While the United States' testing capacity has increased in recent months, public health experts say the nation is still struggling to test enough people to properly track the spread of the virus. That's why researchers have begun to explore alternative ways to track the new coronavirus and identify potential hot spots. The latest testing method gaining traction among researchers and infectious disease experts relies on sewage systems.

    According to STAT News, wastewater epidemiology has previously been used to detect polio in other countries and opioid misuse in the United States. Now, researchers are looking to employ the strategy to detect Covid-19. "We know that SARS-CoV-2 [the virus that causes Covid-19] is shed in stool, which means it can be collected in sewage systems," said Megan Murray from the Harvard T.H. Chan School of Public Health

    Peter Grevatt, CEO of the Water Research Foundation, said in recent weeks several labs have demonstrated the method's ability to detect the virus' RNA in wastewater—and the data suggests it could be used to predict future hotspots as states ease social distancing guidelines and prepare to reopen their economies, STAT News reports.    

    For instance, in Connecticut, researchers found that the amount of the virus' RNA in sewage between March 19 and May 1 was highest about one week before cases in New Haven reached its peak, Science News reports.

    And researchers in France that used wastewater tracking in Paris found the rise and fall of confirmed Covid-19 infections between March 5 to April 23 aligned with the amount of the virus detected in the sewage system. "Viral genomes could be detected before the beginning of the exponential growth of the epidemic," and "a marked decrease in [viral RNA] was observed" when cases fell, the researchers said.

    "Wastewater offers the opportunity to provide near real-time trend data," according to Mariana Matus, CEO of Biobot Analytics. "It can provide … the opportunity to mass-test up to 75% of the U.S. population on a regular basis at a fraction of the cost of clinical testing."

    Experts looks to ramp up wastewater testing programs in US

    Some countries—including Finland, Germany, and the Netherlands—have already launched national wastewater surveillance programs for Covid-19. But in the United States, these large-scale efforts have yet to take off.

    Grevatt last week told congressional staffers that his foundation is working to identify labs to participate in a quality control test to establish credibility for a national testing method in the United States. Grevatt said water utility companies across the county are already conducting their own analyses.

    "We hope to have results of this lab-to-lab comparison by the end of the summer,” Grevatt said.

    A spokesperson for CDC told Politico that the agency is considering employing wastewater testing for Covid-19, but clarified that the agency is "not conducting any testing" at this time.

    That's in part because researchers are still exploring the method. Biobot, which is currently working with about 400 water facilities across 42 states to test the wastewater method, said a previous test on wastewater from Massachusetts found high levels of the virus, but it was unable to determine how many Covid-19 cases could be in the area. Matus said they could only "distinguish between 10 and 100" cases.

    "Work is moving in a direction where you may be able to count the cases in a community, but we aren't there yet," Grevatt said. According to STAT News, researchers must first discern at which point during infection does it appear in stool; how the amount of virus detected differs among severe, mild, and asymptomatic cases; and whether water quality can affect the results (Begley, STAT News, 5/28; Garcia de Jesus, Science News, 5/28; Swan, et al., Politico, 5/1; KTLA5/Los Angeles Times, 4/29).

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