COVID in wastewater: How it can predict surges, and what Texas COVID sewer data shows
COVID-19 wastewater surveillance, an early warning system for the emergence of coronavirus in communities, hints at the possibility of another COVID surge despite numbers of positive tests trending downwards.
In Texas, the seven-day average number of new daily COVID cases has dropped below 2,000, compared with more than 50,000 daily in mid-January during the height of the omicron variant surge. The state’s seven-day average for daily COVID deaths has dropped below 40 as of early March.
But sewer data offers public health officials a better understanding of COVID-19 trends before they become apparent by capturing the presence of infections with or without symptoms. And it signals the rate of coronavirus transmission before testing or hospitalization.
Officials then know where to allocate mobile testing and vaccination sites. And hospitals have a chance to prepare for potential crowding.
“Estimates suggests between 40 and 80% of people with COVID-19 shed viral RNA in their feces, making wastewater and sewage an important opportunity for monitoring the spread of infection,” said Dr. Amy Kirby, team lead for the National Wastewater Surveillance System, at a CDC briefing.
The program was introduced in September 2020, but ramped up in February, with 482 testing clusters in several states providing data.
What does Texas data say?
In Texas, there were 39 wastewater sampling sites supplying data from March 2 to 16. They’re in Galveston, Harris, Fort Bend, El Paso, Dallas and Hardin counties.
In the past 15 days, virus levels found in wastewater have increased at 18 of the Texas sites. Levels have fallen at 21 test sites.
Tarrant County’s current community level of COVID is considered low, according to the CDC.
What does the U.S. data look like?
Of 482 test sites across the country, 188 showed increases in virus levels in the past two weeks; 118 of those showed increases of 100% or more.
See a map of the U.S. with current wastewater testing data here.
Could we see another COVID surge?
It’s too early to say there will be another surge, says UT Southwestern researcher Dr. Jeffrey SoRelle. But it is a possibility.
“This virus continues to fluctuate up and down continually,” SoRelle said. “So it’s inevitable that it probably won’t go down forever. But the timeframe over which that’s gonna happen is hard to say without a lot more information in this area.”
While wastewater data is helpful, he said, we don’t have enough sites in place throughout the state that could indicate community trends.
“I think that it is something that we’ve seen happening like in the U.K. and some areas of Europe, where they’re sort of seeing a turnaround of cases that were decreasing that started increasing again lately within the last week or two,” SoRelle said. “So things that often happen over there can happen over here as well, or tend to, at least.”
This story was originally published March 20, 2022 at 2:47 PM.
