It is well recognized that most emerging diseases of humans are zoonotic, and that the forces working to create emerging diseases in humans are also operating in animal populations. However, what is often overlooked is that emerging human diseases are usually preceded by the emergence of the same pathogen in an animal population. In fact, the developing disease in animals acts as a link allowing the disease to take hold and wreck havoc in public health. Numerous examples--Rift Valley fever, monkeypox, Nipah, and Ebola--serve to underscore this linkage and to highlight the increasing interconnectedness of animal and human health.
Emerging infections in animals—potential new zoonoses?