Studies with cell free virus are needed to define infection—there is no proof yet of safety or danger

Xenotransplantation is the transfer of viable cells, tissues, or organs between species. It has been proposed as a solution to the shortage of human organs (allografts) to treat people with organ failure. There are still serious immunological barriers to the broad clinical application of this technology. Concern has centered on the risk of introducing novel pathogens derived from animals into human recipients of xenografts. In addition, there is the possibility that these infections could spread from the xenograft recipient to the general population. At present, few data address the degree of risk for such interspecies infections in humans.

Infectious diseases are common after organ transplantation, largely due to the immunosupressive agents given to prevent graft rejection.1 The risk of infection may be greater in xenograft recipients because of the possible need for greater levels of immune suppression and the role of novel pathogens from animals. 2 3 Many lists of “potential human pathogens from swine” have been created, ranging from lists of organisms likely to cause disease in transplant recipients who are immunosupressed to exhaustive lists of every organism known to infect pigs.

Many organisms may be excluded from closed herds of …