Researchers trying to learn what killed the first person to receive a heart transplant from a pig have discovered that the organ contained a viral DNA. However, they are not sure if the virus played a part in the death of the recipient, 57-year-old David Bennett.

The University of Maryland doctors said they did not find signs that this bug, called porcine cytomegalovirus, was causing an active infection.

Bennett died in March, two months after the ground-breaking experimental transplant.

A major worry about animal-to-human transplants is the risk that it could introduce new kinds of infections to people.

Because some viruses are “latent,” meaning they lurk without causing disease, “it could be a hitchhiker,” Dr. Bartley Griffith, the surgeon who performed Bennett’s transplant, told The Associated Press.

For decades, doctors have tried using animal organs to save human lives without success. Bennett, who was dying and ineligible for a human heart transplant, underwent the last-ditch operation using a genetically modified pig’s heart to lower the risk his immune system would rapidly reject such a foreign organ.

Griffith said his patient, while very ill, had been recovering fairly well from the transplant. His condition deteriorated one morning as he woke up with symptoms similar to an infection. Doctors ran numerous tests to try to understand the cause, and gave Bennett a variety of antibiotics, antiviral medication and an immune-boosting treatment. But the transplanted heart became swollen, filled with fluid and eventually quit functioning.

Doctors at other medical centers around the country are experimenting with animal organs in donated human bodies and are anxious to attempt formal studies in living patients soon. The discovery of the virus in the pigs heart may affect those plans.
-AP