Tuesday marks the milestone of five years since the World Health Organization labeled COVID-19 a pandemic.

Some of the first people to feel the impact were health were healthcare workers in Chicago and around the country and world. Five years later, some health care looked back on those early days of the pandemic — and some of the changes to health care that are here to stay.

Stepping into the Medical Intensive Care Unit at Northwestern Memorial Hospital, there is a stillness usually found only in times of pattern and routine.

But five years ago, the space was in the process of being transformed into Northwestern's COVID ICU — at a time when everything was intensely new and unknown.

"The first days were intensely scary," said Northwestern clinical nurse Emily Collins. "I remember looking out from the glass doors that we have in our ICU and thinking, 'OK this is going to be big.'"

It was bigger than the staff could have imagined. They found themselves having to make personal sacrifices.

"I spent almost a year away from my family," Collins said.

Some staffers even had to move out of their homes.

"My son has childhood asthma, so actually, the hospital allowed us to stay in hotels," said Northwestern respiratory therapist Ravi Fernando. "So I was in a hotel for about almost three and a half months. Never went home."

Fernando volunteered to work on the frontlines.

"It was a little scary at the beginning, because we don't know if there's a cure for that pandemic," he said.

With five years hindsight, the Northwestern medical staffers said it is hard to believe so much time has passed.

"It feels sort of crazy," Collins said. "To some degree, it feels like it just happened, and other way, it feels like it was 20 years ago."

That feeling is a common one.

"Everybody was saying it feels like it was yesterday, and it also feels like it was a lifetime ago," said Dr. Susan Russell, medical director of the Medical Intensive Care Unit at Northwestern.

That may be maybe some experiences stay with them — reigniting familiar feelings during the recent spikes in respiratory illness like RSV and flu.

"You know, there are still sometimes and still some instances and occurrences where I'm like, 'Oh, that feels like a little bit of COVID just came back," Collins said.

The World Health Organization said COVID no longer fit the definition of a "public health emergency" in May 2023.

Northwestern started a peer-support program to help frontline workers during the toughest times. Leaders said that program continues and has been expanded to include more staff.