The 57-year-old patient who survived two months after undergoing a landmark pig heart transplant may have died of a pig virus, his transplant surgeon announced last month.

In January, David Bennett, a handyman who suffered from heart failure, underwent a highly experimental surgery at the University of Maryland medical center in which doctors transplanted a genetically modified pig’s heart into him.

Shortly after undergoing the surgery, Bennett died in March. The hospital simply said his condition had worsened over the span of a few days but did not provide an exact cause of death.

Last month, Bennett’s transplant surgeon, Bartley Griffith, revealed that the pig’s heart was infected with a porcine virus known as porcine cytomegalovirus, which may have contributed to Bennett’s death. In a webinar hosted by the American Society of Transplantation on 20 April, Griffith described the virus and doctors’ attempts to treat it, MIT Technology Review first reported on Wednesday.