Colorado will use wastewater sampling at a handful of individual buildings, including schools and hospitals, this fall to see if it can produce information about COVID-19 that participants can actually use.
Since the summer of 2020, the state has been looking for the genetic material of the virus in municipal wastewater systems to get an idea of how many people are infected.
As of early July, 53 utilities serving about half the state’s population were sampling twice a week. Colorado’s 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 nasal swab tests, sewage sampling cannot identify whether someone has the virus. But since people shed the virus in their feces, whether they have symptoms or not, it gives an idea of how many cases go undetected because people feel fine or can’t get to a testing site, said Rachel Jervis, a epidemiologist who leads the wastewater project at the Colorado Department of Public Health and Environment.
“We can remove the human behavior component,” he said.
Testing a building might not yet identify who has the virus, but it would provide more accurate information than municipal surveillance, which collects waste from all sewer-connected homes and businesses 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 ahead without that money, Jervis said.
The health department did not specify how many places could participate, but said some schools have shown interest. Hospitals and other health facilities are also likely partners, spokesman Brian Spencer said.
It’s possible that in the future the sewage data will also help the state track other viruses or bacteria, though they haven’t made a plan to look for specific diseases, Travanty said. Some cities have begun testing for monkeypox, which is something Colorado is considering, she said.
The big question, when testing for COVID-19 or any other pathogen, is whether people can ultimately do something with that information, Jervis said. In schools, that could mean doing more individual testing to identify which students are contagious or encouraging vaccinations when the virus is widespread, he said.
By looking at a small number of people, such as those who work in a building, the amount of virus in wastewater can vary dramatically, Jervis said. In those situations, it’s particularly important to compare the results with other measures, such as the number of known cases and the percentage of tests that came back positive, he said.
There is a similar problem with rural areas, because many people use septic systems and they are not taken into account in the tests.
“We don’t see (wastewater) as an independent monitoring system,” he said.
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