RICHMOND, Va. (AP, WRIC) — The Virginia Department of Health is monitoring sewage in an effort to predict future outbreaks of COVID-19.

VDH’s Environmental Technical Services Manager Dr. Marcia Degen said the state recently launched a central monitoring program that will screen samples from 25 geographically diverse utilities on a weekly basis.

VDH’s Wastewater Surveillance Program Manager Dr. Rekha Singh said testing sewage can help health officials gauge COVID-19 infection in a community. She said people who are sick shed the virus in bodily waste about five to seven days before showing symptoms.

The goal is to provide warnings before an outbreak begins.

“This is cost effective because we can take a community pool sample at once instead of taking a sample from each and every patient,” said Singh. “We can give advanced warning.”