Organ Transplantation, Risks

Viruses are among the most common causes of opportunistic infection after solid organ and hematopoietic stem cell transplantation (SOT and HSCT). Viral infection is associated with both direct (invasive disease) and indirect (immune modulation) effects affecting susceptibility to other infections and promoting allograft rejection. The transplantation recipient is susceptible to a broad array of viral pathogens. Some may be transmitted with the allograft as donor-derived infections, while others result from exposure, either soon after the transplant or from more distant exposures when infection is latent and reactivates in the setting of immune suppression. Simultaneous infections with multiple viral or viral and nonviral pathogens are common. The risk for viral infection is a function of the intensity of exposure and virulence of the specific virus, the intensity of immune suppression used to prevent graft rejection or graft-versus-host disease, underlying immune deficits, and factors affecting host susceptibility. Studies of viral latency, reactivation, and of the cellular effects of viral infection will provide clues for future strategies in prevention and treatment of viral infections. This article covers specific issues relating to viral infection in SOT and HSCT; additional details regarding these viral infections are also found elsewhere in this text.