MIAMI >> Alix Zacharski, a nurse manager, went to check on one of her patients inside the COVID-19 intensive care unit at Miami’s Jackson Memorial Hospital on a recent afternoon, hoping that the patient, who had been struggling to breathe on her own, would be a little better. But these days inside the COVID ICU, almost everything is worse.

The week before, Zacharski’s team had lost a 24-year-old mother whose entire family had contracted the coronavirus. The woman, like every other patient in the COVID ICU, had been unvaccinated.

Zacharski reached the sliding doors of her patient’s room and peered inside.

“We intubated her?” she asked a doctor. “When? This morning?”

“Yesterday afternoon,” he said.

“Jesus,” Zacharski said, her voice a near whisper.

COVID patients have never stopped arriving at Medical ICU-B., the unit that Zacharski has tended since March 2020. But the onslaught of admissions had slowed. For a glorious period, the unit had shrunk to three patients. The end of the pandemic seemed within reach.

Now patients fill the ICU’s eight beds again. A second unit, with 50 additional beds, opened this week.

The resurgence of the coronavirus has burdened hospitals anew across the country, with a rush of patients fueled by the virus’s virulent delta variant catching doctors off guard. Florida has reported the highest daily average hospitalizations in the nation, 36 for every 100,000 people over the past two weeks, according to data compiled by The New York Times. In Jacksonville, hospitals have more COVID patients than ever before, despite the availability of vaccines.

Health workers such as Zacharski feel disbelief that they must endure another surge. She remains tired from the previous one. And she cannot get her head around having to treat patients the same age as her adult children who are gasping for breath because of a preventable infection.

Last year, Zacharski feared the unknown. How bad would SARS-CoV-2 be? Could doctors treat it? What would the darkest days of the pandemic look like?

Now she is armed with hard-earned knowledge from the past 14 months — and vaccinated, as a sticker on her hospital badge boasts. But the virus continues to move into uncharted territory.

“We are scared of seeing what we saw, and this time affecting the younger population,” she said. “This is the hardest thing I’ve ever done in my entire career.”

Jackson, Florida’s largest public hospital, had 232 COVID patients Friday, still half the 485 it had July 27, 2020, its pandemic peak. But a sharp rise in recent hospitalizations prompted administrators to limit visitors and warn that more stringent measures could soon be necessary.

About 61% of Miami-Dade County residents are fully vaccinated, higher than the state average of 49%. Miami-Dade holds one of the highest vaccination rates among the nation’s large, socially vulnerable counties, those characterized by high poverty rates, crowded housing and poor access to transportation.

But even high vaccine coverage may hide large gaps in immunity — among younger or working people, for example, who are vaccinated at lower rates — that can trigger outbreaks, said Jennifer Nuzzo, a public health researcher at Johns Hopkins University’s Bloomberg School of Public Health.

Jackson CEO Carlos Migoya said the vaccination rate among the hospital’s employees — 60% as of Thursday — was too low, a problem plaguing many hospitals, which have started to mandate the shots. At Jackson, 91% of third-year resident physicians have been vaccinated, but only 37% of patient-care technicians.

Jackson has also admitted some vaccinated people, but almost all have been transplant patients with compromised immune systems. During last week’s visit by a reporter and photographer from The New York Times, none were in the ICU.

Inside the hospital’s main COVID ward, known as South Wing 7, Victor Suero, 34, shared a room with another young man, a privacy curtain drawn between their beds. A loud pump sucked air out through the window to create negative pressurization.

Two days earlier, Suero, a power lineman with a mermaid tattoo on his right arm, had run a 102.5-degree fever. He had been recovering from leg surgery and called his doctor, who told him to get to the Jackson emergency room, where he tested positive.

Suero said he had not gotten vaccinated for several reasons: He lived until recently in a less densely populated part of Pennsylvania. His mother and sister were vaccinated. And he felt protected by his youth and generally good health.

“I just thought, ‘I’m a healthy person, so I don’t need to go and get it right away,’” he said from his bed, four boxes of apple juice on his lunch tray. “I’m just not really for it.”

His illness still felt like a “really bad cold,” he said, but he worried it would interfere with other surgeries he needs: “It has been a pain in the butt to deal with this.”

In retrospect, did he wish he had gotten a vaccine?

“Honestly, I still feel the same,” Suero said. “Maybe so that I don’t have any more complications with my leg and surgeries coming up — that would probably be the only reason why I would get vaccinated. But had it not been for this, I probably wouldn’t be looking to get vaccinated.”

However, he added: “I hope nobody else gets COVID, ‘cause it sucks.”

In the COVID ICU, no patients could speak because all eight of them — six under the age of 50 — were intubated.

Monitors beeped. A box lay on the floor, stuffed with bags of clear fluid to clean kidneys should they start to fail. Posters outlined tips on how to turn patients prone on their stomachs to help them breathe.

A year ago, to avoid contagion from going into patient rooms, cables stretched to IV monitors in the hall, Zacharski recalled. Doctors and nurses wore protective suits that made them look like astronauts. Now the equipment remained inside, and the staff dressed in scrubs and N95 masks.

Zacharski, 52, came to Florida seven years ago from Michigan. She had immigrated as a young woman from Colombia, married a man from Poland, learned Polish and raised two Michiganders, now 28 and 29.

She paused outside the room of the woman Dr. Jheison Giraldo had intubated the previous afternoon. Giraldo recalled cracking jokes with the woman, trying to ease her anxiety as she gulped for air on her second day in the ICU.

“I was trying to make her feel lighthearted,” he said. “I got her to smile. And then a couple of hours later, she’s almost falling asleep because she couldn’t breathe.”

“It’s terrible to watch,” Giraldo added. “It’s like watching somebody drown. It’s horrible.”

Zacharski lingered on the thought.

“It’s the worst feeling ever,” she said. “When you watch somebody looking at you like, ‘I can’t breathe, help me.’ And that’s the worst image that I have in my mind. I never forget it.”

Then Zacharski took a breath and looked in on the next patient.

This article originally appeared in The New York Times.

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