Which term refers to diseases that exist in animal populations but can affect human health?

The term that specifically refers to diseases that exist in animal populations and have the potential to affect human health is "zoonotic." Zoonotic diseases are those that can be transmitted from animals to humans, either directly or indirectly. Understanding zoonotic diseases is crucial in both veterinary and human health, as these pathogens can lead to significant public health challenges.

On the other hand, the other terms do not encapsulate this concept. "Exotic" typically pertains to diseases that are not native to a particular geographic area and have not been previously reported there. "Emerging" refers to diseases that are newly recognized or increasing in incidence or geographic range, but it doesn’t specifically imply a direct link to animal sources. "Transboundary" relates to diseases that cross borders and affect multiple countries, primarily focusing on the movement aspect rather than the zoonotic potential.

Thus, "zoonotic" is the most appropriate term for diseases originating in animal populations that can impact human health.