Trends from the Houston Health Department’s COVID-19 wastewater monitoring project indicate a decrease in virus across Houston, mirroring the city’s dropping viral positivity rate and further validating the project as a potentially faster method to identify and contain the disease.

The project, a partnership with leading wastewater and data scientists from Rice University and Baylor College of Medicine, tests wastewater from the city’s 39 treatment plants for the presence of SARS-CoV-2, the virus that causes COVID-19. People who have COVID-19 shed virus in their feces, regardless of symptoms.

The data can help identify emerging outbreaks and pinpoint precise locations for interventions to break chains of transmission.

“The City of Houston has worked hard to educate and empower the public about COVID-19 and stop the virus from spreading in our community. This innovative project equips the Houston Health Department with localized data that indicates where a COVID-19 outbreak may be occurring before it shows up in viral test results,” said Houston Mayor Sylvester Turner. “Ultimately, the goal is an early warning system that allows the health department to identify problem areas sooner and put measures in place to slow the spread.”

Wastewater testing started in May and resulted in additional viral testing at several congregant living centers in the city. The health department will soon begin testing wastewater at Houston long-term care facilities.

“Tracking the virus in wastewater provides an unbiased estimate of the extent of the virus compared with relying solely on clinical testing,” said Dr. Loren Hopkins, chief environmental science officer for the Houston Health Department and professor in the practice of statistics at Rice University. “The hope is to continue using this method to help inform public health decisions regarding interventions to control the virus.”

In addition to identifying emerging outbreaks, wastewater data can detect disease resurgence in communities, is more cost effective than mass testing surveys, and provides data in areas with limited viral testing.

“Testing wastewater is a faster and cheaper way to monitor community health compared to testing individuals,” said Dr. Lauren Stadler, assistant professor of civil and environmental engineering at Rice University and academic lead of the project. “This approach is a powerful tool that doesn’t require any individuals to opt-in and provides a way to measure both asymptomatic and symptomatic cases. Viral load in wastewater is an early indicator of one to two weeks in what we will see in the community's clinical positivity rate."

“Researchers in the City of Houston pioneered these approaches of looking at wastewater during the terrible polio epidemics that plagued Houstonians in the 1940s – 1960s, thus helping create the field of environmental virology. That great legacy continues with this project,” said Dr. Anthony Maresso, associate professor at Baylor and founder of BCM TAILOR Labs.

Areas of the city with higher concentrations of the virus in wastewater can be targeted for increased testing, outreach, and education.

“At a time when fewer people are getting tested, this project helps us see what’s happening in the city,” said Dr. David Persse, local health authority for the Houston Health Department. “People still need to go out and get tested, but this project gives us data that serves as another tool to identify disease, slow the spread, and save lives.”

The wastewater project is not a substitution for viral COVID-19 testing. Houstonians should visit HoustonEmergency.org/covid19 for current, free COVID-19 testing sites and information about protecting their family and community from the deadly virus.

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