Gov. Tim Walz is urging Minnesotans to stick with mask-wearing as the constant in the state's COVID-19 response, even as other strategies change against a pandemic that now has caused more than 4,000 deaths statewide.

The governor thanked Minnesotans on Monday for a recent hike in mask-wearing, based on survey data, and said it should be a bridge for the state to a COVID-19 vaccine.

\"It makes sense to everyone, being this close to a vaccine, to try and reduce those infections the best we can,\" he said.

Walz addressed the public as the state reported Monday a total of 4,005 COVID-19 deaths, including 21 new deaths. The jump from 3,000 deaths took 20 days, compared with the three months it took to go from 1,000 to 2,000 deaths and the nearly two months to increase from 2,000 to 3,000 deaths.

The state has reached 356,152 infections with the novel coronavirus that causes COVID-19, including 5,296 infections reported Monday. But the latest pandemic wave has shown signs of easing.

State leaders on Monday also announced that Minnesota would comply with new guidance by the U.S. Centers for Disease Control and Prevention to allow for shorter quarantine periods following viral exposures.

Quarantining for 14 days remains the surefire way to prevent the virus from spreading. But the new guidance allows people to resume normal activities after 10 days if no symptoms emerge, or after seven days if they have negative diagnostic test results.

While there remains a slight risk of spreading the virus 10 days after exposure, a shorter quarantine might increase compliance, Walz said.

\"If we could get more people ... to quarantine for 10 days even, that would have an impact on the spread of the virus,\" he said.

Walz said information on initial COVID-19 vaccine distribution will be released Tuesday and that he hoped to make an announcement this week about what happens after a current four-week closure of bars, restaurants, fitness clubs and entertainment venues ends on Dec. 18.

Despite political divisions over mask-wearing, the rate of Minnesotans who always wear masks in public has risen from 57% on Sept. 1 to 74%, according to survey data published by the Institute for Health Metrics and Evaluation (IHME) in Washington state.

Carnegie Mellon University's COVIDcast showed a comparable increase from 86 to 95% in the rate of Minnesotans who said they wear masks most or all of the time.

People increase mask-wearing in response to rising COVID-19 levels in their communities, either on their own or because of government mandates. But that can come too late to prevent a wave of infections, said Ali Mokdad, an IHME researcher.

\"We're paying for it right now, even with our best behavior,\" he said. \"It's kind of too little, too late, for certain locations.\"

Modeling by IHME predicts 7,900 COVID-19 deaths in Minnesota by April, but 6,958 if 95% of people always wear masks in public.

The CDC on Friday updated its guidance, recommending \"universal\" mask-wearing in all public indoor locations. The announcement followed a CDC report the previous week that found a drop in COVID-19 in 18 Kansas counties that embraced a mask mandate against an increase in 81 other counties in that state.

\"Keeping the vaccine on the side, I would say masking is our single most important strategy for preventing COVID-19,\" said Dr. Elie Berbari, chairman of the infectious diseases division at Mayo Clinic. \"But it works only if everybody does it. I think that is the key. It doesn't work if some people wear the masks and other don't.\"

The CDC in its recommendation cited several studies showing at least modest benefit from mask-wearing. State health officials stressed that masks aren't protective alone and need to be paired with other public health measures such as social distancing.

Studies also have found more evidence of masks offering \"source control,\" meaning they work best if people who are infected wear them to protect others.

Mayo researchers recently used mannequins and particle generators to simulate the predominant method of transmission of the SARS-CoV-2 virus: droplets spread when people cough, talk or breathe.

In results late last month, Mayo reported that mask-wearing by an infected person offered protection to someone 3 feet away, but more protection at 6 feet. Mask-wearing by the source and recipient offered the most protection.

Around half of infected people have no symptoms and can spread the virus anyway, which underscores the need for masks, Berbari said.

\"It's hard to know when you will be exposing somebody,\" he said. \"Nobody is going to do it intentionally.\"

Not all research has found conclusive benefits of mask-wearing. The U.S. Agency for Healthcare Research and Quality (AHRQ) regularly reviewed mask-related research through October and found inconclusive proof that masks protected people in community settings against SARS-CoV-2, despite evidence that they worked against other viruses.

However, Dr. Christine Chang, medical officer for AHRQ's Evidence-based Practice Center, said there is \"anecdotal evidence of that benefit, and people making decisions about mask use may use that evidence and other available resources to encourage the practice.\"

A Danish study compared COVID-19 rates between 2,392 people who wore masks for a month and 2,470 who didn't. Illness rates were 1.8% for mask-wearers and 2.1% for those who didn't wear masks — a statistically insignificant difference of about 16%.

Berbari said that study focused on protecting the wearers, when most of the benefit appears to come from infected people wearing masks to protect others.

COVID-19 activity surged in November, but the positivity rate of testing in Minnesota declined from 15.5% on Nov. 10 to 11.2% on Nov. 26. The number of COVID-19 patients filling intensive care beds in Minnesota hospitals declined from 394 on Nov. 30 to 362 on Dec. 6.

The spike in infections happened as surveys suggested Minnesotans were increasing their mask usage. State health officials said respondents might have been thinking about mask-wearing during daily errands. Unpublished state survey data shows that mask-wearing was less common during group social events that have been catalysts for viral spread.

\"Minnesotans are doing a better job wearing masks when they're in public settings, running errands, but they self-report that they are less vigilant about mask wearing when they are in social gatherings,\" said state Health Commissioner Jan Malcolm.

Jeremy Olson • 612-673-7744