Last month, a new COVID-19 variant from the omicron family spread across Oregon, causing a seventh wave of infections.

On paper, this seventh wave hasn’t looked particularly impressive, peaking in late May at about 1,500 new cases reported per day. But data from sewage samples collected at wastewater treatment plants across the state suggests that the BA2 omicron variant is silently causing far more infections than are showing up in state testing tallies.

“Wastewater across the state is more or less at record highs or near record highs,” said Tyler Radniecki, an associate professor of environmental engineering who is leading the wastewater sampling research effort at Oregon State University.