Twin Cities wastewater data suggests omicron peak may be past

A long line of people standing while waiting with masks on.
People wait in line at a testing site to receive a free COVID-19 PCR test last month in Washington, D.C. In the Twin Cities, the metro area's wastewater data suggests that the latest COVID-19 surge fueled by the omicron variant may have turned a corner.
Anna Moneymaker | Getty Images 2021 file

Updated: 5:45 p.m.

The surge of new COVID-19 cases that has battered the Twin Cities metro area since Christmas may have turned a corner. That’s according to an unorthodox source: the metro’s poop.

Scientists with the Met Council and the University of Minnesota’s Genomic Center have been analyzing Twin Cities wastewater for more than a year, and have found that levels of COVID-19 viral material in the wastewater closely predicts what traditional case counts will show. This data — newly released to the public following an MPR News request — showed COVID levels in Twin Cities wastewater starting rising around Dec. 22, a week before case counts started their spike.

Now the latest data finds COVID levels in metro wastewater peaked around Jan. 10 and then started falling. 

COVID load in Twin Cities metro wastewater.

That’s “great news,” said Dr. Matt Binnicker, the Director of Clinical Virology at Mayo Clinic in Rochester, Minn. 

“We have done some wastewater testing locally, and it seems that the positivity in wastewater samples usually precedes the case positivity by a net five- to seven-day range,” Binnicker said. “So if that wastewater positivity is starting to show a decline, then we can expect actual COVID cases to show a decline about a week after that.”

But it could take longer than usual to see that peak in case counts. COVID-19 test processing is currently seeing unprecedented delays, a combination of sky-high testing demand and lab workers themselves home sick or quarantining. 

As a result, the daily reports from the Minnesota Department of Health have become more erratic. It’s currently hard to discern meaningful trends in any case data more recent than eight or nine days — a problem exacerbated by the disruption to the normal reporting schedule from Monday’s holiday.

Average age of newly reported COVID cases in Minnesota.

If accurate, the wastewater data would show the omicron surge peaked in the metro area about three weeks after it started rising. That matches up with what’s been seen in other places who faced omicron surges before Minnesota did.

A peak in the metro area’s COVID-19 outbreak would also not necessarily mean the rest of the state is out of the woods. The Twin Cities area saw cases spike in late December, about two weeks before most of greater Minnesota. That could mean greater Minnesota will see its peak about two weeks after the Twin Cities does, or somewhere around Jan. 24.

New COVID-19 cases per capita by region in Minnesota

Binninger said Mayo’s modeling suggests Minnesota could hit its case peak in the next week or two.

The Met Council’s wastewater data is available online here.

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