Interest in using wastewater surveillance to monitor Covid-19 continues to grow in the United States, as the values of the early detection tool come into clearer focus.

In September 2020, the US Centers for Disease Control and Prevention launched the National Wastewater Surveillance System, investing millions of dollars in an effort to coordinate and build upon programs that track coronavirus in samples collected in sewage systems.

Participation in the program has risen steadily since launch. But what's driving interest now -- and has led to the biggest bump yet -- is the change in clinical testing strategies across the US, said Amy Kirby, a microbiologist who leads the CDC's wastewater program.

With the growing prevalence of at-home Covid-19 tests and the public's waning interest in testing in general, less case data is being officially reported. Local health departments are "recognizing that clinical surveillance isn't going to have as much information about what's going on in the community," she said.