Colorado is going to use wastewater sampling in a handful of individual buildings — including schools and hospitals — this fall to see if it can produce information about COVID-19 that the participants can actually use.
Since summer 2020, the state has looked for the virus’s genetic material in municipal wastewater systems to get an idea of how many people are infected.
As of early July, 53 utilities serving about half of the state’s population were drawing samples twice a week. The Colorado public health lab can also use those samples to determine which variants are most common, said Emily Travanty, director of the state’s public health lab.
Unlike testing with nasal swabs, wastewater sampling can’t identify whether any individual has the virus. But since people shed the virus in their stool whether they have symptoms or not, it gives an idea of how many cases are going undetected because individuals feel fine or aren’t able to get to a testing site, said Rachel Jervis, an epidemiologist who leads the wastewater project at the Colorado Department of Public Health and Environment.
“We can kind of remove the human behavior component,” she said.
Testing in one building still wouldn’t be able to identify who has the virus, but it would allow for more precise information than municipal surveillance, which pools waste from all of the homes and businesses hooked up to sewer service in an area.
The state health department applied for a grant from the Centers for Disease Control and Prevention to set up a pilot program, but the project could go forward without that money, Jervis said.
The health department didn’t specify how many locations might participate, but said a few schools have shown interest. Hospitals and other health facilities are also likely partners, spokesman Brian Spencer said.
It’s possible in the future that wastewater data will also help the state track other viruses or bacteria, though they haven’t made a plan to look for any specific diseases, Travanty said. Some cities have started testing for monkeypox, which is one thing Colorado is considering, she said.
The big question, when testing for COVID-19 or any other pathogen, is whether people can ultimately do anything with that information, Jervis said. In schools, that might mean doing more individual testing to identify which students are contagious, or encouraging vaccinations when the virus is widespread, she said.
When looking at a small number of people — such as those working in one building — the amount of virus in the wastewater can swing drastically, Jervis said. In those situations, it’s particularly important to compare the results with other measures, like the number of known cases and the percentage of tests coming back positive, she said.
There’s a similar problem with rural areas, because many people use septic systems and aren’t accounted for in the testing.
“We don’t see (wastewater) as a stand-alone surveillance system,” she said.
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