An American woman has become the world’s longest-living person to receive a pig organ transplant.

The woman received a pig kidney transplant 61 days ago. She is currently the longest-living person to receive an organ transplant from an animal.

Towana Looney, 53, received the experimental organ last November after being on the transplant waiting list for nearly eight years with little hope of finding a suitable donor organ.

After Looney received a kidney from a pig, she stayed in the hospital for only 11 days. The woman will now remain in New York under medical supervision for another month before returning home to Alabama. Four more Americans managed to obtain pig organs with the altered gene, but none of them lived for more than two months.

“If you saw her on the street, you wouldn’t think she was the only person in the world walking around with a functioning pig organ inside,” said Dr. Robert Montgomery of Langone Health, who oversaw the transplant.

Doctors say the success of Looney’s operation has led the medical team into uncharted territory. They carefully monitor the patient’s condition because they do not understand what problems may still arise.

Scientists hope that genetically modified pig organs could be a solution to the acute shortage of donor organs for transplantation. Around 7,500 people are on the transplant waiting list, according to the UK’s National Health Service. Last year, more than 415 people died before undergoing surgery.

There are more than 100,000 people in the United States in need of a transplant, and most of them are waiting for a kidney transplant.