Pig Virus 'Hitched a Ride' Into Man Who Got Pig's Heart

The first person to receive a heart transplant from a pig may have also been the first person to be killed by porcine cytomegalovirus—a virus normally only found in pigs that was detected in patient David Bennett 20 days after the transplant. The surgeon who performed the groundbreaking procedure, Dr. Bartley Griffith of the University of Maryland School of Medicine, says the virus apparently "hitched a ride" into Bennett, the New York Times reports. Officials say the pig, which was specially bred to reduce the risk of organ rejection, was repeatedly tested for the virus, but the nasal swabs would only have detected an active infection, not a latent one where the virus is present in organs but not replicating.

Bennett died two months after the surgery. Griffith says the 57-year-old initially tested negative for the virus. A "blip" so low it was considered a possible error was detected after 20 days, and after Bennett became extremely ill 40 days in, tests showed that the virus had been multiplying extremely rapidly, triggering a severe immune system response called a "cytokine storm." The cause of Bennett's death has not been confirmed, but during a webinar last month, Griffith said the pig virus "maybe was the actor, or could be the actor, that set this whole thing off." Determining the cause of death will be vitally important for future attempts to transplant animal organs into humans, MIT Technology Review reports.

Some scientists believe Bennett could have survived much longer if not for the virus. Joachim Denner of the Institute of Virology at the Free University of Berlin says that in his team's experiments, baboons given pig hearts lived for months if the organs were virus-free but if the virus was present without a pig immune system to fight it, the baboons only survived two weeks. He says the virus can easily be removed from pig populations. The herd Bennett's organ came from was supposed to be guaranteed virus-free, Griffith said. MIT notes that some researchers fear that accidentally transferring pig viruses to people could start a new pandemic if the virus adapts, though there is no sign the porcine virus infected any of Bennett's human cells. (More organ transplants stories.)