RICHMOND, Va. (AP) — The Virginia Department of Health will be monitoring sewage in various parts of the state in an effort to predict future outbreaks of COVID-19.

The Danville Register & Bee reported Saturday that VDH is deploying up to 25 wastewater monitoring sites across the commonwealth.

That’s according to a recent report from the University of Virginia’s Biocomplexity Institute, which collaborates with state health officials. The report does not state where those monitoring sites will be. But VDH has been polling utilities to assess their willingness to participate in a sampling program.

Testing sewage can help health officials gauge COVID-19 infection in a community because people who are sick shed the virus in bodily waste, even if they’re not showing symptoms. Combined with other programs that monitor COVID-19 infection in communities, the goal is to provide warnings before a surge begins.

This kind of testing of wastewater isn’t new. It’s been used for other infectious diseases, such as polio, VDH said.