SAN FRANCISCO (AP) — Zully Broussard thought she was going to help one person by donating a kidney.

Instead, she helped six.

The Sacramento woman’s donation to a Benicia man set off an organ swap that resulted in five more sick people getting new kidneys at a San Francisco hospital. Three transplants were planned for Thursday, and the remaining three Friday.

“I thought I was going to help this one person who I don’t know, but the fact that so many people can have a life extension, that’s pretty big,” Broussard said.

Domino-like kidney swaps are still relatively new but are becoming increasingly common.

With a total of a dozen patients and donors, this week’s surgeries at the California Pacific Medical Center represent the largest kidney donation chain in its transplant center’s 44-year history, hospital spokesman Dean Fryer said. The patients at are between 24 to 70 years old, and most are from the San Francisco Bay Area.

Transplant chains are an option when donors are incompatible with relatives or friends who need kidneys.

In this case, six donors are instead giving kidneys to strangers found through a software matching program developed by 59-year-old David Jacobs, a kidney recipient whose brother died of kidney failure. Its algorithmic program finds potential matches using a person’s genetic profile.

Jacobs, of San Francisco, said he understands first-hand the despair of waiting for a deceased donor.

“Some of these people might have waited forever and never got the kidney,” he said. “But because of the magic of this technology and the one altruistic donor, she was able to save six lives in 24 hours.”

Fewer than 17,000 kidney transplants are performed in the U.S. each year, and between 5,000 and 6,000 are from living donors, considered the optimal kind.

Kidney swaps are considered one of the best bets at increasing live-donor transplants, and they are becoming more common as transplant centers form alliances to share willing patient-donor pairs. The United Network for Organ Sharing has a national pilot program underway.

In 2001, Johns Hopkins Hospital in Baltimore, Maryland, performed a transplant chain that started as a two-way kidney exchange and grew to 30 pairs.

Jacobs’ kidneys failed in early 2000 from a genetic disease. In late 2003, a living unrelated donor provided an organ for a transplant.

A new chance at life got him thinking.

“I talked to my doctor about kidney-paired donation. He was excited about the idea but didn’t know how to do it,” he recalled. “I was a tech person. I’ve been in technology my whole professional career. I thought of it as an enterprise software problem I could solve.”

He said the two months he imagined it would take to take to develop the software stretched into six years.

The National Kidney Foundation reports more than 100,000 people in the United States are awaiting kidneys, and 12 people die a day while waiting.

Broussard said her son died of cancer 13 years ago and her husband passed away 14 months ago, also from cancer.

Asked why she volunteered to donate a kidney to a stranger, the 55-year-old said: “I know what it feels like to want an extra day.”