What term describes a highly contagious disease with the potential for rapid spread across borders?

The term that accurately describes a highly contagious disease with the potential for rapid spread across borders is "transboundary." This term specifically refers to health concerns or diseases that can cross national boundaries and pose risks to multiple countries. Transboundary diseases often require coordinated international responses due to their ability to spread quickly among populations, making them a significant focus for global health organizations.

In contrast, the other terms have different implications in the context of disease spread. "Endemic" refers to diseases that are consistently present within a specific geographic area or population. "Exotic" typically denotes diseases that are rare or not commonly found in a specific region, often imported from other places. "Cosmopolitan," while it can suggest widespread or diverse elements, does not specifically capture the essence of disease transmission across borders in the same way that "transboundary" does. Therefore, transboundary is the most appropriate term for describing the situation outlined in the question.