Houston has detected the omicron variant of the coronavirus in eight of its wastewater treatment facilities, city health department officials said Tuesday. And that type of surveillance — which Dallas has not taken on — has helped Houston officials recognize that the new variant is spreading in multiple parts of the city.
Though the plants where omicron was found represent only about one-fifth of the city’s 39 wastewater treatment plants, the plants aren’t concentrated in one area.
“[The facilities with the omicron variant] are scattered throughout the city. That tells us, more than likely, that the variant is here, circulating in the community already,” said Scott Packard, chief communications and public affairs officer at the Houston Health Department.
SARS-CoV-2, the virus that causes COVID-19, can be shed in the feces of people with COVID-19, sometimes days before a person develops symptoms. The city’s detection of the omicron variant in wastewater samples was first reported by the Houston Chronicle.
On Monday, a 40-year-old Harris County woman tested positive for the variant, becoming the first confirmed case in Texas. She was fully vaccinated and had no recent travel history, Harris County officials said.
As of Tuesday, no one else had tested positive for the new variant in the city of Houston, Packard said.
The health department is conducting the wastewater surveillance for COVID-19 in partnership with researchers at Rice University and Baylor College of Medicine. Wastewater testing cannot identify individual people who have COVID-19, but it can identify neighborhoods with particular virus variants or relatively high virus loads.
Dallas County is not participating in similar wastewater surveillance to track the virus, said Dr. Philip Huang, director of Dallas County Health and Human Services. He said he doesn’t know of any other organizations or municipalities in North Texas that are operating similar programs.
While Dallas County previously considered using wastewater surveillance, the price of creating such a system was too high. “It’s actually quite expensive to set that up,” Huang said.
The North Texas Municipal Water District took part in a nationwide survey in the spring of 2020 to test wastewater for COVID-19.
“After the 10-week survey, [the water district] discontinued its participation in the study due to inconsistent data that required continuous interpretation by local and state public health officials,” said Kathleen Vaught, public relations specialist at the water district.
Public health experts have long used wastewater samples to track the growth and spread of bacteria and viruses, like the poliovirus.
The Centers for Disease Control and Prevention began discussing the use of the tool to study COVID-19 in February 2020.
By September of that same year, the CDC and the U.S. Department of Health and Human Services launched the National Wastewater Surveillance System, also known as NWSS, to help state, tribal and local health departments track and respond to COVID-19.
Because people with COVID-19 can shed the virus in their feces days before symptoms start, it can give municipalities a jump start on virus outbreaks.
“So, you can see levels [of the virus] spike in the sewage before you get a massive outbreak,” said Dr. Timothy LaPara, a University of Minnesota professor of civil, environmental and geoengineering who studies COVID-19 in wastewater. “It’s a couple of days to a week’s advance notice...”
Wastewater samples positive for the virus can also be genetically sequenced to determine which variants are present.
Houston is the only Texas city to participate in the NWSS, although that could change as the program grows in the next month, said NWSS team lead and CDC microbiologist Dr. Amy Kirby. Data taken from Houston wastewater samples is submitted to a national database tracking similar data from nearly 400 utilities across the country.
The University of California, Merced’s Naughton Lab created and maintains a dashboard, called COVIDPoops19, to track global wastewater testing for the virus.
The Houston Health Department uses wastewater data to identify priority areas for intervention, said Dr. Lauren Stadler, an assistant professor at Rice University’s Department of Civil & Environmental Engineering.
“They have a lot of information right now that they’re using to direct resources across the city,” she said. “Wastewater is playing an increasingly critical role in helping identify specific areas that are experiencing high infection burden or increases in cases.”
The department then sends “strike teams” to certain ZIP codes to work with community leaders to encourage testing and vaccination efforts, Stadler said.
