Minnesota surpassed 13,000 COVID-19 deaths this week with the toll still falling hardest on the elderly, unhealthy and unvaccinated.

The coronavirus remains capable of surprises, though, as it veers to vulnerable locations or demographics or mutates into variants that threaten new populations. This week's state COVID-19 update revealed a new twist: Women outnumber men in COVID-19 deaths this summer.

Women made up 45% of the 12,649 deaths before June, but 55% of the 323 deaths reported so far this summer.

Historically, women follow public health precautions such as mask-wearing more rigidly and outpaced men in COVID-19 vaccine uptake last year, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. Waning immunity and a lack of follow-up with booster shots this year could heighten exposure risks now.

"You can come up with 100 different reasons why women may be more exposed now," he said, "perhaps because they were more diligent about not being exposed earlier (in the pandemic). But it's not clear."

Still, mortality risks have declined for men and women since the winter. That trend is reflected in the 171 days it took for COVID-19 deaths to increase from 12,000 to 13,000 — with Thursday's total reaching 13,014. The preceding millenary jump to 12,000 deaths took only 34 days. At peak severity, COVID-19 caused 1,000 deaths in 14 days in Dec. 2020, before vaccine was available.

State health leaders are hopeful that COVID-19 deaths will continue to decline, and said the elevated share of deaths among women is based on low numbers and perhaps is a statistical oddity. The death rate nationally remains higher among men.

"With vaccine, with therapeutics, with all of the advances in ... prevention and treatment of COVID, I think there is reason to be optimistic," said Kathy Como-Sabetti, manager of the COVID-19 epidemiology section of the Minnesota Department of Health.

Yet risks remain. Jeanine Dunbar resolved to protect her sister, Monica Doxtater, who had a hard life before the pandemic and needed care in assisted living for health problems before she was 60. Doxtater was vaccinated. On outings, they always wore masks and usually chose takeout over restaurant tables. Sometimes, they risked crowds for favorites, like cotton candy and corndogs at the Midway of the Minnesota State Fair.

Pandemic levels were low in Minnesota in late April when a rapid test instantly showed that Doxtater had COVID-19. Dunbar was crushed. Chronic obstructive pulmonary disease from a lifetime of smoking didn't help Doxtater, and her damaged lungs failed to heal after a month in intensive care. She died June 2 at 54.

"I tried to protect her from this ugly disease," Dunbar said, "but she got it anyway."

Men outnumbered women in COVID-19 deaths for 22 consecutive months until June in Minnesota. The gender gap was most extreme in fall 2021 when men made up more than 60% of state COVID-19 deaths. More aggressive uptake by women of newly available booster doses could have contributed to the gap at that time, amid the spread of the severe delta variant.

Age is a clearer risk factor — with 82% of the state's COVID-19 deaths amongseniors since the start of the pandemic. The rate dropped to 71% in the second half of 2021, when health officials believe a lack of vaccinations among nonelderly adults left them susceptible to the delta variant. But as deaths have declined this year, those that remain predominantly have involved seniors — including 89% since May.

Ethel Kilde reached 100 before dying of COVID-19 on June 1, according to state death records. Her obituary described her work as a World War II air traffic controller, a nurse's aide in Grand Rapids and a restaurant owner in Hewitt. She raised four children with her first husband and remarried after his death, becoming a beloved figure in the lives of four stepchildren.

Kitty Yonker died two days later and two years to the month after her husband died of COVID-19. Yonker and her husband had been an inspiration, coming from small towns in West Virginia and Wisconsin and meeting by earning National Science Foundation scholarships to attend Harvard University.

Yonker remained at home for years to raise her two sons, while her husband taught math at Breck School in Golden Valley. But she went back to school in midlife to become a nurse practitioner and work in public and school health roles. Although her health at 86 had been declining, Yonker anticipated many more years and dreamed with her family about travels yet to come.

"It for sure cut her life short, cut my dad's life short," said their oldest son, Rick Yonker, of White Bear Lake.

Chronic health problems long have been associated with elevated risk. A state review of 24,765 COVID-19 hospitalizations in Minnesota showed that 76% involved patients with underlying conditions. Among that group, 60% had hypertension and 42% were obese. The death rate among hospitalized patients in the review was 9%.

Past COVID-19 outcomes don't offer much clarity about the future, though, Osterholm said. The past two years involved wild swings in deaths and hospitalizations, but those numbers have settled since the winter. Minnesota has averaged five COVID-19 deaths a day for three months.

"What we had seen in the previous part of the pandemic was these big mountain peaks and then these big valleys," Osterholm said. "We've kind of hit the high plains, the plateau."

Como-Sabetti's optimism for fewer deaths is placed partly in the rate of immunity developed by vaccination and recent infection. The latest federal analysis of pediatric blood tests for various medical procedures indicates that 74% of Minnesota children had been infected with the coronavirus by late April. The CDC stopped posting an estimate based on adult blood tests, but health officials believe it is comparable.

"I would hope that would put us in a better place but I wouldn't entirely count on that part of it either," she said. "We still need to be prepared that we may have surges."

The BA.5 coronavirus strain that is causing most COVID-19 cases right now has shown an ability to break through immunity and infect people, but it hasn't caused as much severe illness as other variants. The worry would be a more severe variant that could similarly break through the immunity shield, Como-Sabetti said.

Vaccines remain a key source of protection against COVID-19 deaths and hospitalizations, even if coverage has waned, she added. During severe pandemic waves last winter, unvaccinated seniors were 12 times more likely to die from COVID-19 than seniors who had received initial doses plus booster shots. This summer, unvaccinated seniors in Minnesota still are almost four times more likely to die of COVID-19, according to the latest state breakthrough data.

Dunbar is grieving for her sister, a partner in so much fun and trouble when they were kids. She carries the guilt of putting the first cigarette in her sister's mouth, and the trauma of seeing Doxtater struggle for breath at the end. Dunbar didn't seek a COVID-19 vaccine herself until she saw her sister's suffering.

"I do not want to be like that," she said, "so I went and got vaccinated."