COVID-19 levels decline 30% in Twin Cities wastewater

Coronavirus levels in Twin Cities wastewater have declined 30% over the past two weeks, offering a glimmer of optimism heading into the fall and winter.

Friday's report from the Metropolitan Wastewater Treatment Plant in St. Paul was one of the first signs of change, in either direction, after a summer in which COVID-19 levels have been relatively low but stagnant in Minnesota.

The decline "is a statistically significant movement to a lower level, suggesting fewer COVID infections in the Metro Plant service area," said Steve Balogh, a research scientist at the treatment plant. However, he cautioned that "we can't predict whether this trend will continue or reverse itself."

In the first two years of the pandemic, fall coincided with increases in COVID-19 levels that led to severe winter pandemic waves that challenged hospital capacity. Broad immunity levels as a result of vaccination and recent infections could be changing the outlook this year.

Infection data released Thursday by the Minnesota Department of Health showed some progress — with the seven-day average of new infections dropping below 1,400 per day on Aug. 18 for the first time in a month.

Infection data for more recent days is incomplete, but Mayo Clinic's 14-day forecast for Minnesota predicts continued progress in September.

Wastewater analysis for viral levels is considered a leading indicator of pandemic activity because it isn't affected by the number of COVID-19 tests performed.

Wastewater sampling results published by the University of Minnesota show stable or declining viral levels in the rest of the state as well. Sampling by 13 wastewater plants on the fringes of the Twin Cities metro area showed a 35% decline in viral levels since Aug. 28.