COVID-19 infection numbers have declined at Minnesota's colleges and universities over the past month even as they have surged statewide.

Dashboards for colleges in Minneapolis, St. Paul, Winona, Mankato, and Moorhead showed similar COVID-19 spikes in late September followed by lower, but steady levels of infections in October.

Minnesota campus health officials said Tuesday that students are getting the message about mask-wearing and social distancing, and that rapid contact tracing and quarantines are preventing outbreaks from surging.

"When I walk around campus, students are all wearing masks, they're all social distancing, they appear by every measure to be adhering to the protocols," said Madonna McDermott, a student health administrator at the University of St. Thomas in St. Paul, which reported 17 positive cases last week, compared to 56 in the week ending Sept. 25.

College students are at low risk for severe COVID-19, but their sociability and mobility make them ideal incubators for spreading the virus to one another and then to older and frailer people at greater risk.

The Minnesota Department of Health has reported 2,368 COVID-19 deaths and that more than 80% have involved people 70 or older. More than 72% involved residents of long-term care facilities as well — though that disparity evened this summer. Eleven of 15 deaths reported Tuesday involved private residences.

Proof of the college student risk came this month from the Gundersen Medical Foundation in La Crosse, Wis., where genetic sequencing of viral samples linked outbreaks in local colleges and long-term care facilities.

In a prepublication study, Gundersen researchers showed that infections among students at three local campuses involved two genomic substrains of the SARS-CoV-2 virus. That indicated that their infections occurred locally rather than back home.

"It was the behavioral issues once the students returned — the culture of getting together and having big, prolonged drinking parties that really led to the rapid spread of the virus," said Paraic Kenny, a lead author of the study and director of Gundersen's Kabara Cancer Research Institute.

Similar but subtly advanced viral substrains in two nursing homes, where two residents died from COVID-19, suggest their outbreaks emanated from the college students, Kenny said.

How much college reopenings in Minnesota contributed to renewed COVID-19 activity this fall is unclear.

The Minnesota Department of Health on Tuesday reported another 2,178 confirmed and probable infections, bringing the total in the pandemic to 137,536. The current seven-day positivity rate of diagnostic testing increased to 7%, indicating broader spread of the virus, regardless of any increase in tests performed.

Total COVID-19 patients admitted to Minnesota hospitals increased from 614 on Monday to 657 on Tuesday.

The state's pandemic dashboard showed that 165 of the hospitalized COVID-19 patients were in intensive care, but that total ICU usage in Minnesota declined slightly. Only 997 of the state's immediately available 1,466 ICU beds were occupied by patients with COVID-19 or other unrelated medical issues.

State infectious disease director Kris Ehresmann said the rising infection and positivity rates underscore the growing concern of social and large group events fueling outbreaks. Minnesota has now recorded 244 outbreaks in large group social settings, including 71 weddings and 73 social gatherings. Including 19 outbreaks so far in October, weddings have been directly linked to 667 infections.

Ehresmann said people need to avoid large gatherings, wear masks, and be thoughtful about holiday plans that could spread the virus within family and friend groups.

"At the level of transmission that we're seeing right now in the community, things that may have been relatively safe a month or two ago may no longer be safe," she said.

COVID-19 growth statewide juxtaposes with the stable infection numbers at colleges. Winona State University had issued a two-week quarantine order in September, after reporting 121 new infections in the first week of that month, but it only reported 15 new infections in the week ending Oct. 18.

The University of Minnesota earlier this month relaxed student restrictions — with new infections dropping from 120 in the last week of September to 46 in the week ending Oct. 17.

"This virus is relentless and we must all remain diligent and continue to work together," said Jill DeBoer, director of the U's Health Emergency Response Office. "We cannot be certain of how COVID-19 will impact our campus in the future. However, we can say that we are fortunate to be in the position we are in today."

Kenny said mitigation efforts may have helped, but COVID-19 also might have burned quickly through the cavalier students on college campuses.

"It blazed through them pretty quickly and now that all of the low hanging fruit, from the virus' point of view, have been infected, there is probably a population that are still sensitive but have developed good precautionary measures," he said.

Two studies published Tuesday by the U.S. Centers for Disease Control and Prevention offered further evidence of the risks of viral spread among college-age students. One showed the ease with which COVID-19 spread in two university soccer teams in Chicago amid numerous group social events. The other showed that teenagers and young adults are the least likely to follow mitigation strategies, though over time they have been quicker to increase their mask usage than other age groups.

Minnesota college leaders said they want to prevent complacency from setting in, and reduce odds of infections spreading when students return home for midterm and holiday breaks.

McDermott said a new ad campaign on campus will encourage students at St. Thomas to remain diligent, and to consider diagnostic testing followed by 14 days of reduced activities or quarantines so they return home infection-free for the holidays.

"Just re-emphasizing to pay attention, follow the protocols," she said, "and think about getting tested before going home."