Why hospitals in several states are reinstating mask requirements

Some hospitals across the United States are reinstating indoor masking rules amid rising cases and hospitalizations of respiratory illnesses including COVID-19 and influenza.

Hospitals in at least six states -- California, Illinois, Massachusetts, North Carolina, Washington and Wisconsin -- have put masking guidelines in place, according to an ABC News count.

Over the weekend, Mass General Brigham, which is the largest health system in Massachusetts, told ABC News it issued guidelines requiring employee caregivers and those working in patient care areas to wear masks.

Another Massachusetts hospital, Dana-Farber Cancer Institute, told ABC News it reinstated its masking requirement on Dec. 18 due to higher rates of respiratory illnesses.

Additionally, Cook County Health, which has hospitals and community health centers in and around Chicago, wrote on its website that it began requiring masks for all staff, patients and visitors aged 2 and older in waiting rooms and patient exam rooms on Dec. 26

What's more, a Los Angeles County Public Health order, requiring all health care personnel to wear masks while in contact with patients or working in patient care areas, went into effect after the county's COVID-19 hospital admission level hit the "medium" threshold, meaning between 10 and 19.9 new COVID-19 hospital admissions per 100,000.

Dr. John Brownstein, an epidemiologist and chief innovation officer at Boston Children's Hospital and an ABC News contributor, said hospitals are full of patients and staff at risk of severe illness, which is why mask guidelines have been reintroduced as cases rise.

"Ultimately, health systems, hospitals, places that deliver care are going to see some of the most vulnerable and at-risk individuals -- many, with underlying conditions," he said. "Those are especially the places where we want to protect individuals and so when we have this rapid rise in respiratory illness, those are going to be the first places to try to use measures to reduce chances of transmission, both to protect patients, those receiving care, as well as workforce."

Data from the Centers for Disease Control and Prevention (CDC) shows 31 states, plus Washington, D.C., are experiencing '"high" or "very high" levels of respiratory illness activity, described as people visiting their primary care office or the emergency departments with respiratory complaints such as fever, sore throat or cough

During the week ending Dec. 23, the latest date for which data is available, there were 29,059 new weekly hospital admissions due to COVID-19, according to the CDC. It marks the seventh consecutive week of increases and the highest figure reported since late January 2023.

Meanwhile, there were 14,732 new hospital admissions linked to influenza for the week ending Dec. 23 compared to 9,930 the previous week, CDC data shows.

Brownstein said the increase is not surprising given that the U.S. is in the middle of respiratory virus season in combination with recent holiday travel and gatherings.

"While there's nothing unusual about what we're seeing, the data still reflects an increase in illness and, as we know, masking will be helpful, regardless of the respiratory pathogen: RSV, COVID, flu, and the other respiratory pathogens that are circulating," he said." So, it's sort of a one size fits all strategy."

Because an increase in respiratory illnesses risks putting a strain on the health care system, Brownstein recommends staying home when sick and seeking care if symptoms worsen or do not improve.

"Of course, we're in a situation where there's a lot of illness out in the population, but we want to make sure that we limit the impact on hospitals and save care for those who especially need it," he said. "If people need to use emergency department, they absolutely should, but we're in a moment now where capacity definitely is a big topic of focus for hospitals that are trying to both maintain their ability to take care of patients with severe illness as a result of these pathogens, but also be able to manage routine care as well."

ABC News' Youri Benadjaoud, Dr. Chris Medrano and Sony Salzman contributed to this report.