A Colorado hospital brought back mask mandates as flu hospitalizations surged. Will others follow?

With about four months remaining into the flu season, Denver7 brought concerns from the community to hospital officials about the measures hospitals are taking to stymie nosocomial flu infections

DENVER — As the number of weekly flu hospitalizations in Colorado skyrocketed to levels not seen in more than 20 years at the end of year, doctors at UCHealth were discussing how the hospital would treat patients if things got any worse. At Banner Health, hospital leadership was more proactive.

With just a few hours left before the clock struck midnight on Dec. 31, the Arizona-based hospital implemented mandatory universal masking at all of its facilities across the six-state health care system, including Colorado. That means all patients, visitors and staff will be required to wear masks where patients are present until further notice.

“This measure is necessary because older patients and those with immunodeficiencies are at heightened risk and these extra precautions will help safeguard our most vulnerable populations,” said Dr. Marjorie Bessel, Banner Health’s chief clinical officer, in announcing the measures. “Our top priority is to protect our patients, staff, and the communities we serve by reducing the spread of the virus.”

Banner Health officials attributed the protocols, not seen since the end of the public health emergency for the coronavirus pandemic in the spring of 2023, to the rise in cases from a new variant of the H3N2 flu strain this year called subclade K.

The variant, which was spotted in the summer, is causing more infections as people encounter it for the first time, which means more cases than prior years and more emergency department visits compared to seasons past. Luckily, there’s been no evidence to suggest subclade K is more severe than other circulating strains of the flu, according to the World Health Organization (WHO).

Though it may not be more severe than other H3N2 flu viruses out there, the strain is known to cause higher rates of hospitalizations and longer hospital stays, especially among older adults. This year, however, H3N2 has hit children especially hard, according to the most recent data published by the U.S. Centers for Disease Control and Prevention (CDC).

“We’ve really seen an unprecedented year in terms of influenza cases in children at Children’s Hospital Colorado,” said Dr. Suchitra Rao, a pediatric infectious diseases specialist at Children’s.

Dr. Rao said that across all of the hospital’s different locations, Children’s has had close to 600 hospitalizations so far this flu season, with about 20% of those needing to go to the ICU to receive additional respiratory support. The bulk of those hospitalizations have been among unvaccinated children, she said.

“That is definitely sort of a record number. We’re just seeing many more cases and a lot more severity in terms of people coming into the emergency department and people getting admitted to the hospital,” she said.

Across the state, the story isn’t much different. Statewide data shows Colorado is experiencing a record-breaking flu season.

Though hospitalizations have since stabilized and returned to levels typically seen during a normal flu season, Colorado’s weekly flu hospital visits at one point reached more than 800 — numbers never before seen since the state started tracking the data in 2004.

Overall, the number of Coloradans hospitalized for the flu since October (which marks the beginning of flu season in the U.S.) has also broken records.

Numbers from earlier this month show more than 3,000 people had been hospitalized for influenza — that's more than three times worse than the pre-pandemic average, and more than double what the state saw during the 2024-25 season, the worst year for flu in Colorado since records began.

The bad news? Flu season is only halfway done.

It’s precisely those trends that worry Dr. Maria Gillespie, a CSU professor of mathematics and the founder of Mask Together Colorado, a grassroots advocacy group that aims to promote health equity and layered mitigation strategies, such as mask wearing and cleaner air, in the fight against airborne diseases.

A mother of twins — one of whom is immunocompromised — Dr. Gillespie has been keeping track of Colorado’s unprecedented flu season over the past several weeks. And as someone who suffers from asthma, she took note when Banner Health reinstated universal masking across its hospitals. If Banner Health was doing it, why weren’t other Colorado hospitals moving in the same direction?

Hoping to get answers and help move flu trends downward, her group sent a petition to UCHealth and Children’s Hospital Colorado, asking that they follow the lead of Banner Health by providing and requiring high-quality masks, such as KN95 and N95 respirators, for all patients and staff through the end of the flu season.

Gillespie, who spoke with Denver7 about the petition, said it isn’t just about requiring masks in hospital settings during flu season, but about raising awareness that asymptomatic spread of illnesses can happen between doctors, nurses and patients, and the measures health care professionals can take to protect the community.

She said that while it’s standard practice for hospitals and other health care settings to clean and disinfect surfaces to reduce the spread of influenza viruses, “there’s not a lot of emphasis on protecting the airborne route, cleaning the air.”

“We need clear air in hospitals, not just clean surfaces for the safety of patients,” Gillespie said. “We need this kind of protection, because people are going to the hospital and picking up the flu even if they went there for a broken leg. And that’s not what you want on top of a broken leg.”

The push for better masks in health care settings isn’t being done solely in Colorado. In a letter addressed to the WHO, the World Health Network — a multidisciplinary group of experts — called on the international public health body to update their guidelines “by establishing respirators as the universal default for all healthcare encounters.”

Doing so, the group wrote, would lead to fewer infections among patients and health care workers, as well as less burnout and staffing shortages in health care settings.

While hospital-acquired infections do occur, a systematic review published in 2023 found that influenza infections after visiting a hospital accounted for about 11% of all confirmed infections in a hospital setting over a two-year period.

It’s those types of infections that hospital officials want to prevent as much as possible, given that children and older adults are at greater risk of severe outcomes from the flu.

Denver7 brought Gillespie’s concerns to health officials at UCHealth, Children’s Hospital Colorado and Denver Health, by asking why the hospital systems have yet to implement universal mask mandates given this year’s record-breaking flu season.

Dr. Michelle Barron, the senior medical director of Infection Prevention at UCHealth, told Denver7 that conversations around universal masking did take place between hospital leadership earlier this month, but said decisions around reinstating universal masking are complex and require thoughtful considerations.

“There’s downsides to it, especially for patients that are hard of hearing” and who may not be able to lip read when nurses or doctors speak to them, she said.

Those masking barriers are something Gillespie keeps in mind and knows how to address, as Mask Together Colorado doesn’t just advocate for mask wearing and cleaner air, they also work to educate people on the different types of masks available on the market, like the KN95 BreatheTeq or the OmniMask.