Originally Published: 06 FEB 23 06:01 ET

By Deidre McPhillips, CNN

(CNN) -- At Massachusetts General Hospital in downtown Boston, the hallways of the emergency department are lined with dozens of patients waiting to get a room upstairs.

"Imagine spending days and nights in the hallway under fluorescent lights in the ER next to a trauma bay while [patients] have heart failure, kidney failure or pneumonia," said Dr. Melissa Mattison, a physician and chief of hospital medicine at Mass General, which is a founding member of Mass General Brigham.

"Everybody's doing their best, but where do they go to the bathroom? How do they take a shower if they want to clean up? How do they eat? There's no privacy. It's just, it's awful. It's absolutely awful."

As of Friday, about 87% of all available hospital beds in the state are in use, and capacity strains have eased little despite a dramatic decrease in the number of people being treated for respiratory illness.

"Every day, our emergency room has a backlog of anywhere between 25 and 100 patients waiting for a bed upstairs. So if today, that number was 25, and two weeks ago, it was 100 -- yes, that's better, but there's still a long line," Mattison said. "Maybe the patients aren't piled like sardines in the ER as much when you only have 35 patients waiting compared to 75. But it's still not great."

The winter triple threat of flu, Covid-19 and RSV is easing across the United States, and as in Massachusetts, most states are now reporting low or minimal levels of respiratory illness activity overall.

Nationwide, emergency department visits for the respiratory viruses are a third of what they were a month ago, federal data shows. Flu hospitalizations are nearly as low as they've been all season, since October. Hospitalizations for Covid-19 -- the last of the three viruses to trend down -- have been falling for the past few weeks, and just 4% of hospital beds nationwide are being used by Covid-19 patients.

That's a dramatic shift from January 2022, when Covid-19 patients were filling most hospital beds amid the early Omicron surge. But hospitals are still about as full as they've ever been during the pandemic -- at least three-quarters of available beds across the country were in use for all of 2022 -- and that doesn't seem likely to change any time soon.

Hospitals were facing capacity and resource challenges long before the pandemic hit, experts say, in large part because the people who are being admitted are sicker than they were before.

"It's been a continuing trend over the last decade or so that there's been this greater acuity of patients inside the hospitals," said Nancy Foster, vice president for quality and patient safety with the American Hospital Association. "So what you see is this incredibly sick group of people inside of hospitals. If you're a doctor or nurse or respiratory therapist or pharmacist or any other health professional working inside the hospital, that means it's always a difficult puzzle you're trying to solve to help that patient out."

At Mass General, an emergency department boarder program -- which outlines plans for how to cover patients who were waiting for a bed -- was well-established years before the pandemic hit, Mattison said.

Hospitals started to report capacity data to the federal government in 2020 under a pandemic requirement, so there's no federal data to compare to pre-pandemic years.

But Mattison was quick to say her hospital is 99% full now, like it was in 2019 and years before the pandemic. Still, she says, "how long is that waiting list, and who's on that waiting list? That's something that's not reflected in that metric."

By and large, the mix of patients in hospitals is similar to what it was pre-pandemic, said Aaron Wesolowski, vice president of policy research, analytics and strategy at the American Hospital Association.

As the share of Covid-19 patients drops, it's perhaps "a breath less stressful" for health care providers who felt frustrated by the lack of tools available to help people as they so desperately wanted to in the early days of the pandemic, Foster said.

In fact, for most categories of care -- with infectious disease as a noticeable exception -- the number of people seen in inpatient and emergency department settings in 2022 was lower than it was in 2019, Wesolowski said, citing data from Strata, a health care data analytics firm.

A mix of complicating factors were exacerbated during the pandemic, experts say, straining resources more than ever.

"Length of stay is longer because people are needing more acute care. Because of work force pressures, there are not as many people who can be treated in an inpatient setting all at once," Wesolowski said. "So both things, I think, can be true."

Samuel Scarpino, director of AI and life sciences at Northeastern University, says it's a "perfect storm" of issues: Covid-19 and the ongoing infection control measures that hospitals have to keep in place, a backlog of other patients with a delayed need for acute care, and work force burnout three years into a pandemic.

The biggest risk factor in the equation is still Covid-19, he says, not because a new variant will necessarily cause more hospitalizations but because the unpredictability is forcing hospitals to leave more beds open as a buffer just in case.

"The biggest risk is almost certainly the uncertainty associated with what's coming," said Scarpino, who was previously vice president at the Rockefeller Foundation's Pandemic Prevention Institute.

Foster, of the American Hospital Association, says the pandemic emergency declaration has granted a number of flexibilities -- such as telehealth -- that have helped more patients have options for care that are outside of hospitals.

The federal government has continuously renewed the emergency declaration since January 2020, but it is likely to come to an end in May.

Without it, Foster says, hospitals would probably be even more full than they already are -- particularly as alternative options for care outside of the hospital may become more limited again.

"Part of the reason we have the kind of inpatient hospital capacity that we have right now is that we do have a number of flexibilities that were granted to hospitals by [the Centers for Medicare and Medicaid Services] and other federal agencies and the states during Covid that are being used for a wide variety of patients," she said. "If those were to disappear overnight, we would be struggling to care for the current level of patients."