Now, Dr. Bartley Griffith, director of the Cardiac Transplant Program at University of Maryland Medical Center who performed the transplant, has revealed that DNA from porcine cytomegalovirus, a virus that infects pigs, was detected in the patient prior to his death, according to MIT Technology Review.
"We are beginning to learn why he passed on," Griffith said in a webinar on April 20 discussing the transplant, MIT Technology Review reported. The virus "maybe was the actor, or could be the actor, that set this whole thing off."
Doctors screened the pig's heart for this virus several times. But such tests only pick up active infections, not latent infections in which the virus "hides" in the body without actively replicating, according to The New York Times.
But 20 days after the transplant, blood tests picked up low levels of porcine cytomegalovirus DNA in Bennett's body, the Times reported. At first, doctors thought this could be a lab error. By 40 days after the transplant, however, Bennett became very sick and tests showed a sharp rise in the viral DNA levels in his blood, the Times reported.
Porcine cytomegalovirus is specific to pigs and is not believed to be able to infect human cells. However, the virus might have suddenly replicated out of control in the pig's heart, without the animals' immune system to suppress the virus. This may have set off an inflammatory response in the patient, MIT Technology Review reported.
"Did this contribute to the patient's demise? The answer is obviously, we don't know, but it might have contributed to his overall not doing well," Dr. Jay Fishman, associate director of the transplantation center at Massachusetts General Hospital, who was not involved with Bennett's transplant, told the Times.
More sensitive screening tests of animals will be needed to prevent the transfer of such viruses in future animal-to-human transplantations, the Times reported.