Wastewater monitoring for polio is set to increase in the United States, the Centers for Disease Control and Prevention announced this week.

Sites in Michigan and Philadelphia were identified among the first locations looking at collecting wastewater samples to be tested by the CDC for the potentially fatal, paralyzing virus that surfaced this summer in the U.S. for the first time in nearly a decade.

The CDC said “preliminary discussions” about joining the monitoring effort are underway with other state and local health departments that were not named, as part of a plan to “strategically expand wastewater testing for poliovirus in select jurisdictions across the country.”