Rise in unknown COVID-19 sources amplifies call to wear masks

As Gov. Tim Walz debates whether to mandate mask-wearing in Minnesota, state health officials Friday urged people to don them anyway to slow the spread of COVID-19 and a troubling uptick in mystery cases.

Minnesota has seen a 10 percentage-point increase since June 20 in the rate of infections that state contact tracers can't tie back to likely community sources — such as spouses, co-workers or drinking buddies. The rate of unknown community transmissions reached 34% on July 8, above the state target of 30%.

As more cases come from unknown sources, it prevents health officials from identifying specific individuals with exposure risks and strengthens the need for blanket protections such as mask-wearing and social distancing, said Kris Ehresmann, state infectious disease director.

"We know that a significant number of cases may be asymptomatic," Ehresmann said, so waiting for symptoms to emerge before taking precautions "doesn't necessarily work."

State health officials warned that the rising trend of COVID-19 cases could upset plans to reopen schools in the fall and allow expanded capacities at restaurants and businesses. New COVID-19 cases are being confirmed in Minnesota through lab testing at a rate above 10 per 100,000 people per day now — more than double the state's target rate of 5 per 100,000.

The addition Friday of 669 cases and seven deaths brought the pandemic totals to 45,013 cases and 1,533 deaths. Walz ordered flags at half staff on Sunday, the 19th day of the month, to honor the victims.

State Health Commissioner Jan Malcolm said mask wearing is important but that people still need to follow social distancing guidelines. Bars and restaurants, she added, still need to spread out customers.

State environmental health inspectors have visited and issued guidance to establishments, which could face court closure orders if they don't comply, Malcolm said.

"We're stepping up this enforcement not to play gotcha with restaurants and bars but … to protect both the customers and staff in these establishments and frankly to keep the spread of COVID to a low enough level that we can avoid pretty drastic dialbacks in what establishments are open and how they can operate," she said.

Political dynamic

Mask-wearing amid the pandemic has taken on a political dynamic, with mixed messages by President Donald Trump's administration creating confusion and prompting some of the president's supporters to oppose the practice. Trump has been noncommittal — to the point that his wearing of a mask during a visit to Walter Reed Army Medical Center was national news — but his surgeon general strongly advocates mask-wearing.

Survey results released Thursday by the University of Chicago showed that race, age and underlying health conditions influenced mask-wearing habits but that politics was a strong divider. While 84% of Democrats backed mask mandates, support dropped to 47% among Republicans and 39% among Trump supporters.

Some states and communities require masks in indoor public spaces only, while others require them in outdoor areas where social distancing can't be maintained.

Retailers such as Target and Walmart announced they will require mask-wearing — as will the Minnesota Zoo when it reopens next week.

Some Republican lawmakers wear masks and support the practice but would oppose a mandate by Walz, a Democrat, given the number of businesses and cities taking actions on their own.

"Minnesotans and private entities should be responsible for when and where to wear masks," said U.S. Rep. Jim Hagedorn, R-Minn., adding that the governor should show evidence for masks being effective, listen to opponents in a public forum, and set milestones for withdrawing a mandate before imposing it.

Public weighs in

"Everyone should wear a mask for everyone else," said Kelly, who was mindful of his parents and other elderly people at risk of severe complications from COVID-19.

Kimberly Duke of Prior Lake said it already feels like a mandate with so many retailers requiring masks. (Lunds & Byerlys strongly recommends wearing them.) Mask-wearing seems like delaying the inevitable, she said.

"We need to let the chips fall where they may," she said. "If you're going to get sick, you're going to get sick."

Jolene Moe of Apple Valley and her daughter didn't wear masks entering the Walmart in Apple Valley, but she called herself a "rule follower" who would comply with a mandate.

"I personally feel it's gotten out of hand," she said, though she takes precautions such as social distancing and washing hands.

"A lot of people go on [ventilators] and don't come off them," she said.

The latest state COVID-19 data show that risks increase substantially with age. Among the 24,493 people 39 or younger with known cases of COVID-19 in Minnesota, only 13 have died. Among the 4,549 people 70 or older with known cases, 1,236 have died — a rate of 27%. And 30 of 51 known cases of COVID-19 among people 100 or older have resulted in fatalities.

Protects others

COVID-19 is caused by exposure to a new corona­virus that health officials believe is mostly spread by infected people emitting droplets when they breathe, talk or cough.

People are believed to be at moderate risk if they spend 15 minutes directly within 6 feet of someone who is infected — though more recent research has suggested the virus can be carried through the air in smaller aerosol particles.

"If we could get everybody to wear a mask right now, I really think in the next four, six, eight weeks, we could bring this epidemic under control," wrote Dr. Robert Redfield, director of the U.S. Centers for Disease Control and Prevention, in an editorial this week in the Journal of the American Medical Association.

A review published last month by the U.S. Agency for Healthcare Research and Quality found studies that offered only weak or inconclusive evidence of mask-wearing benefits in public, but other studies have emerged since then.

The CDC this week published a case study showing that masks likely prevented two hairdressers in Missouri who had COVID-19 from infecting their 139 clients.

Public support for a state mask mandate came this week from the Minnesota Hospital Association, with its chief executive, Dr. Rahul Koranne, warning that "we have a narrow window of time to slow the spread of the virus."

"Taking this action universally, rather than city by city or business by business, is important," he wrote.

Hospitalizations for COVID-19 in Minnesota remain at their lowest levels since mid-April. The state on Friday reported that 252 people with COVID-19 were admitted to hospitals, and that 110 needed intensive care.

Health officials are concerned that Minnesota will follow the recent pattern of Southern and Western states in which upticks in mild cases among teenagers and young adults led to spreading the virus to older and more vulnerable people.

The state Health Department early in the pandemic discouraged mask-wearing, mostly to prevent consumers from buying up all of the medical-grade N95 masks that doctors, nurses and others needed for protection while treating COVID-19 patients. The department later strongly advocated the wearing of cloth and non-medical-grade masks.

Ehresmann said the rise in COVID-19 cases from unknown community sources "absolutely" underscores the need for mask-wearing and social distancing.

Only 10% of cases were classified as unknown community transmissions in mid-April, when state health officials were able to trace the majority of infections to families, travelers, food plants and long-term care facilities.

"We're seeing a lot more activity," Ehresmann said, "in which people are mixing and not following the guidance."

Staff writer Jessie Van Berkel contributed to this report. jeremy.olson@startribune.com 612-673-7744 mlsmith@startribune.com 612-673-4788