It’s long been known that many communicable diseases — such as diphtheria, influenza, rabies, anthrax, chickenpox and mumps — were originally diseases of animals, which spread to humans once we began to domesticate them. The general name for such a disease is zoonosis (with plural zoonoses), which derives from the Greek words zoion, “animal”, and nosos, “disease”. As a result of current research into ways to transplant animal organs into humans, the risk of previously unknown diseases transferring with the grafts is greatly exercising medical minds, leading to calls for such techniques to be banned or at least closely monitored until the risk to heath is better known. A disease which might be transferred in this way is a xenozoonosis, using the Greek xenos, “stranger”, in the same specialised sense as it is beginning to be used in words such as xenotransplantation and xenograft, which means “something (transplanted) from a different species”. The adjective is xenozoonotic.