Tracking COVID-19 in San Antonio sewers could help control COVID's spread
An amiable man wearing a San Antonio River Authority cap looked over a sparkling stream teeming with little fish, and laughed.
“I am the grandpa of the minnows,” he said. “I don't let anybody fish down there. Guys go down to get some for bait. They know that's a no-no.”
Sterling Lee has been a treatment superintendent for the River Authority for 34 years.
“Those are protected species out there,” Lee stressed, with another burst of laughter. “Those are my fish. I see guys down there, just no! Get away.”
These fish and this stream are at the end of a water treatment process that begins when one of the 23,000 customers that are served by this plant in Converse, Texas, flush their toilet. The sewage then rushes through plumbing to a point at the other side of this property where it runs through one of three blue tubes into a pool of churning muck where it all mixes together.
It’s from that pool of muck that Lee collected samples for a University of Texas at San Antonio study on whether you could track COVID-19 in a community by regularly testing its wastewater.
“And this is what the treatment plant does,” Lee said. “It represents the community, it represents the areas that we are serving.”
Dr. Vikram Kapoor ran the study from his UTSA lab, and co-authored the resulting paper. The study found that wastewater surveillance is “an effective tool to determine trends in infectious disease prevalence, and provide complementary information to clinical testing.”
Kapoor also concluded that you could use wastewater surveillance to try to get ahead of COVID.
“We call it a leading indicator of surveillance because it can predict before the infection starts spreading. Before people start getting symptoms, before they get tested, they will start shedding the virus in the feces,” Kapoor said. “So if all the people who are infected are shedding the virus, there's a chance that we can pick up that signal days or even a week before they actually get tested.”
Scientists tracking COVID in wastewater in New York City found the same thing. Dr. Davida Smyth is now an associate professor of microbiology at Texas A & M San Antonio, but she was working in New York when the pandemic started.
They were testing the wastewater for COVID and then sequencing what they found to see what variants were there.
“I think the first evidence we had that it was really predictive was when Omicron came about,” Smyth said. “We actually were able to show that it was coming before (it showed up in) people. So it proved that it actually worked.“
Smyth thinks communities all around the world could use this technique to get ahead of new variants and potential surges.
“The data from wastewater gives you maybe two weeks of lead time and what's actually going to appear in the human population,” she said. “So you can say to yourself, ‘Well, a new variant is coming,’ and you can actually look and see where it is in the city and say, 'that's where it's emerging.'”
Then, Smyth said, you could target mask-wearing and other interventions to that specific area, which would be more efficient and effective than locking down entire cities.
Smyth and Kapoor plan to work together to build a surveillance and sequencing program in South Texas, but so far it’s slow going. They’re having trouble getting access to new samples to test, and funding is always in short supply.
Lee would be happy to provide more samples for COVID testing, if he got the go-ahead.
“What I saw from the testing, it was very beneficial,” Lee said.
The Centers for Disease Control has set up a dashboard where states can report the results of their wastewater surveillance, but right now only about a dozen states are sending information. Texas is among them, but only a handful of plants in the Houston area are currently participating.