Monkeypox, a virus that causes painful rashes and flu-like symptoms, is spreading rapidly throughout many parts of the world, including the U.S. To get a fast understanding of how the virus is moving through communities, researchers reporting in Environmental Science & Technology Letters suggest turning to wastewater epidemiology. They show how the method—widely applied to monitor SARS-CoV-2 transmission—could be optimized for monkeypox, potentially detecting as few as seven infections per 100,000 people.