Wastewater sampling suggests that fast-spreading BA.4 and BA.5 coronavirus strains will become the dominant sources of COVID-19 in the Twin Cities, but whether they will disrupt the flat or improving pandemic trends is unclear.

Viral levels in sewage samples from the Metropolitan Wastewater Treatment Plant in St. Paul increased 2% over the past week after declining 38% the prior week. The two emerging variants made up 23% of the viral material found in the wastewater, up from 11% last week, according to new data released by the Met Council on Friday.

The variants were identified in South Africa and caused a surge of infections, even in people with immunity through COVID-19 vaccination or recent infections, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy.

South Africa has "seen many breakthrough infections of people who were infected with BA.1 eight to 10 weeks ago and then got BA.4 and 5 just in the last two weeks," Osterholm said. "The good news is it's a much less serious illness, generally speaking."

The Twin Cities' wastewater results combine with other data to show a muddled picture of the pandemic in Minnesota, ahead of what health officials hope will be a milder summer. Statewide wastewater data maintained by the University of Minnesota shows viral levels flattening in the Twin Cities and in southeast and central Minnesota, but rising in southwest and northeast corners of the state.

Those results match with Thursday's updated risk assessments by the Centers for Disease Control and Prevention, which recommended mask-wearing in indoor public places in 10 Minnesota counties based on their current infection and COVID-19 hospitalization rates.

Nine are in a northeastern block of the state between Wadena and Cook counties, with southeastern Olmsted County being the only one outside that region to have high community COVID-19 levels as well. The entire Twin Cities metro area is now at low risk.

The Minnesota Department of Health on Friday reported another 1,968 infections, and a decline in the seven-day average of new infections that has continued since mid-May but has slowed this week. The results only include publicly reported tests at clinics and state centers and not at-home rapid antigen tests that have grown in availability and popularity.

The state on Thursday encouraged people who already had ordered four free at-home tests to order four more at mn.gov/covid19.

Another 15 COVID-19 deaths were identified on Friday, all in seniors but for one case involving a Blue Earth County resident age 40 to 44. Those additions bring Minnesota's total COVID-19 deaths so far in May to 134 and its total in the entire pandemic to 12,664. Monthly COVID-19 death totals had declined from 1,081 in December to 76 in April before increasing last month.

Hospitals in Minnesota continue to report mixed outlooks, with 446 COVID-19 cases filling inpatient beds on Thursday. That is an increase from a recent low of 183 on April 10. However, many of the COVID-19 cases are considered incidental, meaning the patients were admitted for other purposes and tested positive on routine screenings. The number of patients requiring intensive care increased to 42 on Thursday but still only represented 10% of the total.

At earlier points in the pandemic, as many as 30% of patients hospitalized with COVID-19 needed intensive care because of breathing problems or other complications. Health officials believe recent vaccinations and infections during earlier waves have raised immunity levels, lowering the rate of severe COVID-19 this spring.