For years, third-grade teacher Erin Durga and the custodian at her school exchanged small talk whenever he stopped by her classroom.

The encounters often were brief. Patrick Mertens was, after all, a man of few words.

So it wasn’t until he had to leave school early three days a week for dialysis that Durga and her fellow teachers at Kimball Elementary School learned that the mild-mannered custodian’s kidneys were failing.

To help, they raised money to offset transportation costs to nearby St. Cloud, where Mertens received dialysis treatments. When a Facebook post by his daughter noted that none of his relatives could donate a kidney, Durga stepped up and offered one of hers.

“I knew in my heart that I could do this for someone else,” she said this week. “Pat is a wonderful person and I can’t imagine him not being around.”

Amid the threat of a dire global pandemic, Durga’s gift brought hope.

“She’s an angel,” Mertens said recently after finishing his work in the quiet and largely empty elementary school that recently switched to distance learning because of COVID-19.

Durga, who lives several miles away from this central Minnesota city of 800 people, shrugs off the praise.

“I’m no superhero or angel,” she said. “I’m just a person who did the right thing.”

Across the country, more than 95,000 people a year are waiting for kidney transplants. Only about 9,000 donations are available from deceased donors, which means some in need die before they get transplants, according to national statistics.

Mertens, 64, learned in 2003 that high creatinine levels indicated his kidneys “were bad.” Fourteen years later, his kidneys were failing and a transplant was needed.

The wait for a deceased kidney donor, he learned, would likely be five to seven years.

Dialysis robbed him of time with family and friends, but it kept him feeling OK, he said. He preferred not to dwell on statistics that showed the longer a person is on dialysis, the greater the risk of complications and death.

“Pat was working and quietly suffering,” said Annie Doyle, living donor transplant coordinator at M Health Fairview University of Minnesota Medical Center.

Doyle encouraged Mertens and his family to share his story. Sometimes people respond, raising money to offset medical costs or helping with transportation and meals, she said. Sometimes, someone offers one of their kidneys.

Living donors who are medically evaluated and deemed healthy can lead normal lives because the remaining kidney will compensate for the loss of the other.

For a recipient, a donor kidney from someone who is alive usually functions more quickly and works better than one from a deceased donor, Doyle said.

Although there are some altruistic people who will donate to anyone on a waiting list, most living donors give to someone they know, Doyle said.

If they end up not being compatible, the donor can participate in a paired exchange program to garner a match.

Since 1963, more than half of the transplants performed at the M Health Fairview University of Minnesota Medical Center have involved living donor kidneys and most come from relatives, Doyle said.

Until Mertens’ family put out a Facebook plea, Durga, 38, never thought about being a living donor.

“I didn’t know that there was an organ donor database of people who are willing to donate an organ,” she said.

But Durga had long wanted to do something big for someone else.

“I just never knew how,” she said. “I’m a teacher and I don’t make a lot of money, so I can’t do a lot of things that way.”

Donating a kidney didn’t seem like a big sacrifice, said Durga, an energetic woman who walks four to 10 miles a day to exercise her dog, visit with friends or check in on students who are distance learning. Still, even a minimally invasive surgery to donate a kidney has risks, she acknowledged. And it likely would mean some physical limitations for two months until she fully recovered.

But this could literally save someone’s life, Durga said. “Why wouldn’t you [do it]?” she added.

So amid lockdowns and social distancing to curb the spread of COVID-19, Durga texted Mertens’ wife, who once provided day care to her three children, and said that she was filling out the online forms to be a donor. She eventually became one of the first donors approved by U doctors using a virtual format.

Durga sent them a cheek swab to provide necessary DNA information and spent fours hours in separate online virtual meetings with a nephrologist, transplant surgeon, nutritionist, social worker and transplant coordinator. Then came the in-person meetings, blood and urine tests and imaging work.

As soon as she got word in late spring that she was a match, she stood in Mertens’ driveway to announce the news with a shirt she crafted to say “DONOR.”

“It brought a few tears to my eyes,” Mertens recalled. “I’m not much for expressing myself.”

And he admits he’s not much of a hugger.

“But I had to,” he said. “She was giving me her kidney. It’s quite the honor that someone would give you their kidney. You will appreciate them for the rest of your life. She’s just a wonderful woman.”

The weeks that followed brought some anxious moments for Mertens.

“You don’t know how it’s going to turn out,” he said.

But Durga was always calm, and when Mertens followed her into the hospital July 3 for the lifesaving organ exchange, he felt reassured.

“If Erin could do it, I could do it,” Mertens said.

Months later, the two are back to work and their routines. Mertens is grateful he no longer is tethered to dialysis and his home. He has more time for family and friends and, maybe, a little golfing.

“I can live again,” he said.

Durga is happy to be a part of that.

“I think there are a lot more people like me,” she said. “I think there are a lot of people who want to do good in the world but many don’t see the opportunity.”