The genetically modified pig whose heart was used in a 57-year-old Maryland man as part of a pioneering heart transplant carried signs of a virus that infects the animals, according to the surgeon who performed the first-of-its-kind procedure.

It is believed that the porcine virus may have played the role in the death of the patient two months later, experts said.

David Bennett received the transplant on Jan 7 at the University of Maryland Medical Center in Baltimore. Doctors said that he seemed to be doing well during the first few weeks.

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But, his condition suddenly turned to the worse, the MIT Technology Review reported Wednesday.

“He looked really funky,” Dr. Bartley Griffith, Bennett’s transplant surgeon, said during an American Society of Transplantation webinar. “Something happened to him. He looked infected.”

Despite doctors’ efforts, the patient died on March 8.

Bennett “wasn’t able to overcome what turned out to be the devastating debilitation” caused by the heart failure he experienced before the transplant, Griffith said in a videotaped statement.

Griffith said that subsequent tests showed that the transplanted pig heart was infected with porcine cytomegalovirus. This virus in pigs can cause a wide range of symptoms, from pink eye and sneezing to pregnancy complications and stillbirths.

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The virus previously has been linked to pig organ transplant failures in baboons, the report said.

Griffith said that the virus had not been detected prior to the transplant surgery.

“We are beginning to learn why he passed on,” said Griffith, adding that the porcine ailment “maybe was the actor, or could be the actor, that set this whole thing off.”

The animal was raised by the biotech company Revivicor, which altered its genome to reduce the risk of Bennett’s immune system rejecting the heart.

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The hospital said that Bennett was able to communicate with his family during his final hours.

Joachim Denner, of the Institute of Virology at the Free University of Berlin, said that more accurate testing could address the problem in future animal-to-human transplants.