Viral infections are one of the leading causes of medical complications in transplant recipients.
Sometimes latent viruses, which remain within people's tissue or accompanying cells until reactivated, will infect transplant recipients. But more often, the donor organs are the sources of these viral infections. Although donor organs are carefully screened for infections that are often fatal, such as HIV and hepatitis, it is impossible to exclude organs that test positive for the less-threatening infections that are so prevalent in the population. For transplant patients, EBV can progress to lymphoproliferative disorder, whereby cells multiply out of control, and in some cases, cause tumors. Common examples of these infections, referred to as zoonoses, include rabies and toxoplasmosis, a parasitic infection that is most often spread through cat feces in kitty litter.