COVID-19 virus up 58% in Twin Cities wastewater

Coronavirus levels in Twin Cities' wastewater increased 58% in the past week, indicating that the peak of Minnesota's latest COVID-19 wave remains ahead.

A fast-spreading coronavirus variant — known as BA.2.12.1 and responsible for a surge of COVID-19 in the northeastern U.S. — made up 47% of the viral load in sewage sampled May 10-16 at the Metropolitan Wastewater Treatment Plant in St. Paul. BA.4 and BA.5, the newest variants of concern causing more cases in South Africa, made up 7% of the viral load in the Twin Cities.

Rising viral spread has resulted in more infections — another 2,424 were reported Friday by the Minnesota Department of Health along with three more COVID-19 deaths — but it hasn't produced the level of severe illness that occurred in Minnesota's earlier pandemic waves.

COVID-19 hospitalizations in the state increased to 442 on Thursday, but only 33 patients (7%) required intensive care for breathing problems or other complications. At peak points in the past two years, Minnesota's rate of COVID-19 hospitalizations requiring ICU care was above 30%.

State health officials say they believe immunity from vaccinations and recent infections is helping to reduce the rate of severe illness in the latest wave. However, they urged continued COVID-19 vaccinations because even a low rate of severe illness can exhaust hospital capacity if enough people are infected at once.

Only 49% of Minnesotans age 5 or older are considered up to date with vaccinations, meaning they have completed the initial series and received first boosters when recommended. That number hasn't changed in weeks because the rate of new vaccine recipients is being balanced out by earlier recipients who have declined boosters and lost some immunity against infection.

Wastewater data has become a key to Minnesota's pandemic surveillance because over time it has identified changes in viral spread before COVID-19 case numbers started to rise or fall. The viral load identified at the St. Paul plant this week is the highest since mid-January and is 20 times higher than the low point this year in mid-March.

The increase juxtaposed with the latest aggregate results from 40 wastewater plants across Minnesota that serve about 67% of the state's population. The viral loads from 13 other metro-area treatment plants have declined since last week, according to aggregate results provided by the University of Minnesota. Sampling results can fluctuate among plants, especially if faster-spreading viral variants are more prevalent in some communities than others.