For centuries, humans have looked to water for answers. Ancient Druids used reflective pools for scrying, or predicting the future. Scientists searched for signs of water on planets to posit whether they once hosted life. So maybe it’s not surprising that researchers are looking to water for information about COVID-19. Er, make that wastewater.

Early in the COVID-19 pandemic, Jeff Wenzel received a perhaps unenviable work assignment. Wenzel is the chief of the state’s Bureau of Environmental Epidemiology within the Department of Health and Senior Services. At an annual conference, Missouri Department of Natural Resources employees had heard about countries like the Netherlands that were conducting sewershed testing for SARS-CoV-2. (A sewershed is an area that drains into a particular wastewater collection system.) Because the genetic material from SARS-CoV-2 can show up in human waste—often before symptoms present—researchers can measure the viral load in wastewater. If it’s high, it might indicate the start of an outbreak—or an outbreak that’s getting worse.