(AP) — In early 2020, when the coronavirus began making it difficult for many people around the world to breathe, hospitals became a central front against a disease that, more than a year later, has killed nearly 4 million human beings and counting.

At one hospital in Mission Viejo, Calif., a team of nurses and doctors were recruited for what became the Isolation Intensive Care Unit. Many volunteers at Providence Mission Hospital had come from cardiac and surgical intensive care units, where they deal with death and trauma each day.

Launched in March 2020, the isolation unit would come to be known as “Tip of the Spear,” a military term used to describe a group doing dangerous work. Many nurses who would spend countless hours with patients, helping them return to health or helping them say goodbye to family, got tattooed with spears, hash marks and a heart.

Today, those nurses speak of forming deep bonds and of the joy in helping some deathly sick patients survive. But they also can’t forget horrific and heart-breaking experiences that are very much still with them, even months after the hospital’s special unit shut down as cases in California dropped sharply.

With little knowledge of how to treat patients, and amid enormous personal risks, these nurses had leaped into the abyss. They will never be the same.

To capture the reality that the horrors of COVID-19 will be with us for years to come, even as many countries move beyond the pandemic, Associated Press photojournalist Jae C. Hong turned to an unusual form of photography not typically used in the context of reporting the news. He employed a special exposure technique in photographing 10 nurses in areas of the isolation unit, now empty.

First, Hong made pictures of each nurse. Then he asked them to step aside and shot images of the same background. By using a multiple exposure function, he made the images overlap. The result: pictures that create the feeling that the nurses are both there, in the photo, in the present — and also somewhere else.

Here are their pictures, and the experiences they are wrestling with to this day:

Anthony Wilkinson still thinks about those 30 hours — the ones when three patients died.

The first was a woman who had been on a ventilator for weeks. One day, her oxygen levels dropped sharply and an emergency team began CPR. One lung ruptured, so a doctor inserted a tube in it to begin removing the blood. Then the other lung collapsed. There was no saving her.

That day, the family of a second patient being cared for by Wilkinson decided to withdraw care. The person had been hanging on with the help of a ventilator and medicines.

“You try to keep somebody alive, but their body is decomposing,” says Wilkinson, 34.

Just when Wilkinson’s team was bagging up the body of the second person who died, another patient’s bowel burst. The patient was in a Rotoprone bed, a cage-like, cylindrical structure that rotates patients to improve circulation. “We had to open the cage and bang on his chest. His lungs were already so filled with pressure from the ventilator,” Wilkinson says.

Hours later, the patient died.

Wilkinson says the ICU team and his wife, also a nurse, helped him get through days like that. It also helped that he became a father during the tough year, which allowed him to leave the ICU ward and go home and do “dad stuff.”

The memories, however, linger: “I don’t know if I’ve unpacked a lot of the blood and all the stuff we did to save people’s lives.”

During brutal days at the hospital, Christina Anderson and other nurses would scream or cry together, knowing that at home it would be hard for their families to understand what they were going through.

Still, there was no such thing as leaving their work at the hospital. The stress carried over to loved ones at home who were curious, worried, struggling to understand. Anderson’s 12-year-old would ask: “Mommy, how many lives did you save today?” Or: “Mommy, how many people died today?”

People died and people recovered. But most days, patients were somewhere between the living and the dead.

One of Anderson’s most vivid memories was when five patients were in RotoProne beds. They were in the “bay,” an open post-operative room that could be seen through the window of the anteroom, where nurses would put on personal protective equipment before going in.

Periodically the hospital’s CEO would visit the wing. One day, Anderson asked him if he had seen the bay lately. He had not, so she took him to the anteroom to have a look.

“Oh my God,” she recalled him saying.

“It hit me,” she says, “that what we were seeing and experiencing and how we were treating these incredibly sick patients was anything but normal.”

Debbie Wooters, an ICU nurse for 15 years, vividly remembers a man who had just retired and made big plans with his wife. They had placed an offer on a house out of state. They’d planned to travel.

Each day in the hospital, he got worse. Eventually, he was placed on a ventilator. He died a few days later.

“Instead of looking forward to a new beginning, we were FaceTiming his wife so he could say goodbye and thank her for the lifetime of memories,” Wooters says.

Learning they would be put on ventilators frightened many patients. And naturally so: There were numerous stories of people who had been intubated and never survived. Wooters remembers a patient who “looked at me and said, through his gasping breath, ‘I don’t want to die.'”

“I explained to him that he was in the best hands and we will fight like he was our own family,” she says.

The ICU unit was isolating, not just for patients but for nurses as well. While keeping people alive was the main job, the nurses also needed to keep patients motivated or, when the chance of survival looked less likely, provide comfort.

“There were countless patients that we sat with, talked to, and touched so they knew they weren’t alone while dying,” Wooters says. And then there were the times they connected patients to families via their phones. “The cries and devastation heard,” she says, “was unbearable.”

There were days Lisa Lampkin didn’t eat, drink water or go to the bathroom during her shift. The reason: Going in and out of the isolation unit took time.

It wasn’t just putting on and taking off gowns, gloves and masks, as with regular ICUs. It also required intense hand scrubbing and cleaning her air-purifying respirator, which resembled an astronaut helmet and had its own air system. Then she had to put it back on, scrub her hands again and climb back into the gown and the rest of her gear.

“What was once a 30-second ordeal was now a two-minute ordeal,” says Lampkin, a nurse for 20 years. “And in nursing, minutes are valuable. We remained in the room for hours to allow our patients to have those precious minutes.”

The extra time was needed to overcome communication barriers. Masks and shields muffled words, making it hard for nurses and patients to understand each other. It didn’t help that the patients struggled to breathe, which made talking that much harder.

At the end of each day, Lampkin would weep with joy for making it through her shift without a wave of new patients, or weep with sorrow for all that her patients were enduring.

“I would go home, try to sleep,” she says. Then she would “wake up to the reality of this pandemic again.”

While Elisa Castorena remembers many patients who died, she prefers to focus on happy memories such as working with other nurses to bathe bed-ridden patients while listening to music and joking with them.