Multiple COVID-19 trends have improved in Minnesota over the past week, suggesting a peak in the latest pandemic wave ahead of what health officials hope is another mild summer for the state.

The number of federally designated counties in Minnesota at high COVID-19 risk dropped from 19 to seven, and statewide sampling this week found less evidence in wastewater of the coronavirus that causes the infectious disease. The seven-day average of new infections in Minnesota also declined from 2,138 per day on May 11 to 1,805 on May 20 — although that is only based on publicly reported testing and not any at-home test results.

COVID-19 hospitalizations in Minnesota increased slightly to 416 on Thursday and included 35 people receiving intensive care. The state also reported nine more COVID-19 deaths on Friday — all among seniors — raising its total pandemic toll to 12,628. Both have been lagging trends during the pandemic, though, and health officials hope they will soon follow the other downturns.

Hospitalizations have been less severe in the latest wave — with only 8% of the COVID-19 patients on Thursday requiring intensive care, compared with 30% at earlier points in the pandemic. More patients are being admitted for other purposes and test positive only upon routine screening.

High levels of immunity as a result of vaccinations or coronavirus infections this winter are reducing the severity of illness this spring, said Dr. Matthew Prekker, a critical care medicine specialist with Hennepin Healthcare in Minneapolis.

"The baseline risk in the population for getting so, so sick — that was there before we had widely accepted vaccines — is much lower now," he said. "We're also dealing with less virulent but very transmissible COVID strains ... Fortunately, we're not seeing critical illness nearly as much as we were last year."

Wastewater data was mixed last week, with the University of Minnesota showing steady or even declining viral levels in sewage samples from across the state, but the Metropolitan Wastewater Treatment Plant in St. Paul showing an increase. However, the St. Paul plant on Friday reported a 38% decline in viral load in this week's samples, matching the latest statewide wastewater trends.

Viral levels remained level or slightly higher, though, in wastewater analyzed from six plants in northeastern Minnesota. That matches with the latest regional risk data from the Centers for Disease Control and Prevention, which identified high COVID-19 levels in Koochiching, St. Louis, Pine and Carlton counties.

Freeborn, Olmsted and Winona counties in the south also maintained high-risk CDC designations, meaning that mask-wearing is recommended in indoor public places. The CDC designations, based on infection and hospital numbers, are designed to warn communities when their hospitals could be at risk of bed shortages. Most of the Twin Cities metro area remains at moderate risk, though Anoka and Carver counties are at low risk.

Minnesota's trends match with the northeastern United States, especially in New York where risk levels and case numbers are declining. The latest pandemic wave appears to be trending to the south — with the CDC this week identifying an increase in high-risk counties in states such as Virginia.

COVID-19 levels have declined in Minnesota over the past two summers even as they increased in Southern states, where hot temperatures drive more people indoors and increase their risks of viral transmission.

Health officials warned of wild cards that could disrupt expectations of a mild summer, including even faster-spreading BA.4 and BA.5 variants that were discovered in South Africa and caused rapid increases in infections there. Those two variants made up 11% of the viral load found in wastewater this week in the St. Paul treatment plant, up from 7% last week.

Immunity also wanes with time, and Minnesota is reporting a decline in residents who are up to date with COVID-19 vaccinations — meaning they have completed the initial series and first booster doses when they are recommended.

Only 47% of eligible Minnesotans 5 and older are up to date as of Friday, a decline from 49% last week. Last week's expansion of booster recommendations to include children 5 to 11 caused that rate to go down, because COVID-19 vaccination levels decline with age.