Short-term COVID-19 forecasts remain optimistic in Minnesota, but variant concerns and a surprising uptick in pandemic activity in Europe have left infectious disease experts guarded over the state's long-term future.

The coronavirus load in Twin Cities wastewater declined 8% since last week and dropped to the lowest level since July, the Metropolitan Council reported Friday. The proportion of viral material involving a concerning BA.2 variant increased from 17% last week to 42% this week.

Sewage sampling has become a key barometer, because it has shown over time to anticipate changes in viral activity a week or two before COVID-19 cases rise. The latest levels match other encouraging signs in Minnesota, where the positivity rate of COVID-19 diagnostic testing fell to 3% in the week ending March 10. That's below the state's 5% caution threshold indicating substantial viral spread.

COVID-19 hospitalizations in Minnesota also have declined from a peak of 1,629 on Jan. 14 to 284 Thursday. The state on Friday reported 9 COVID-19 deaths and 538 more infections, but seven-day trends in both categories have steadily declined for two months.

In all, Minnesota has reported 12,321 COVID-19 deaths. The first death, that of an 88-year-old St. Anthony woman, occurred two years ago to the day on Saturday.

Now is the "safest time in many, many months" for friends and families to gather with little fear of COVID-19, said Dr. Dimitri Drekonja, an infectious disease expert with the Minneapolis VA Medical Center. "If you have at all any risk tolerance, now would be the time because you can't predict the future. I think everybody expects that we will have future waves. Whether they are bumps, wavelets or big waves is open for debate."

The most optimistic forecast is that immunity levels from vaccines and recent infections suppress the spread of the virus to the point that it stops being a pandemic and becomes a more manageable endemic.

An increase in cases in Europe despite high vaccination rates has raised concerns, though, and health officials aren't sure if it is happening because of waning immunity or the more-infectious BA.2 variant.

Understanding of the depth and duration of COVID-19 immunity is too limited to make confident projections, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. "We don't know if waning immunity is responsible for what's happening right now in Europe. We don't know what the next variant could be. I'm getting so much pushback from folks saying, 'we can let everything go right now, it's all done.' It could be. Wouldn't that be something? But we could be back in the soup again."

Nationally, 60% of 485 wastewater monitoring sites are reporting declines in overall coronavirus loads and lower infection risks, according to the Centers for Disease Control and Prevention. All seven regions of Minnesota are showing declines, according to the U, which publishes wastewater data from 40 plants accounting for 67% of state residents.

Mayo Clinic COVID-19 modeler Curtis Storlie said a short-term bump in infections is possible but likely to be fleeting. The United States had numerous infections in the latest wave involving the BA.1 omicron variant, and people recovering from that infection appear to have good protection against BA.2, he said.

"We still remain far more concerned about longer term into fall when our immunity from all of these recent infections has waned, while the virus continues to evolve to become more immune evasive," he said.

Minnesota health officials encouraged people to stay up to date with vaccinations, which means receiving the initial series and then a booster when recommended to maintain immunity. While 82% of vulnerable seniors in Minnesota are up to date, the rate declines below 49% for the state's five and older population.

COVID-19 hospitalizations from July through January were 12 times more likely in unvaccinated people than in those up to date with their shots, according to a CDC study released Friday of Minnesota and 13 other states. Hospitalizations were three times more likely in fully vaccinated people who hadn't received boosters.

The omicron variant caused more breakthrough COVID-19 cases than earlier versions. Fully vaccinated people made up 42% of known infections in the second half of 2021 but 62% in the first six weeks of 2022, according to state data.

However, three doses of vaccine provided 94% protection during the omicron wave against COVID-19 death or placement on ventilators, according to a new CDC study coauthored by doctors at Hennepin County Medical Center.

A weary Minnesota is taking advantage of the COVID-19 pause. Two in three Minnesotans were regularly wearing masks indoors in public in late January, according to COVIDcast but that has dropped to one in three.

Mobility has crept up to just 9% below normal, according to mobile device data, and traffic volumes were above expected levels for almost half of January.

The CDC on Thursday listed only Freeborn County in Minnesota in the high-risk range that encourages mask-wearing. The CDC's revised risk assessment is based largely on the burden COVID-19 is placing on local hospitals, which presents problems as an early-warning tool because hospitalizations come later in pandemic waves, Drekonja said.

"This whole theory of 'let's relax and tighten down again when things get worse' is great," he said. "It's just a question of (a) will we detect the things getting worse fast enough, and (b) will people respond to it?"