Which term describes a disease occurrence that affects a very high proportion of the population over a wide geographic area?

The term that describes a disease occurrence affecting a very high proportion of the population over a wide geographic area is "pandemic." A pandemic is not just limited to a specific region; it signifies that the disease has spread globally and impacts many individuals across multiple countries or continents.

To provide context, an epidemic refers to a sudden increase in disease cases above what is normally expected in a specific geographical area. This term is generally used when the disease is localized rather than widespread. An endemic condition, on the other hand, is constantly present within a certain population or region but does not cause widespread illness; it reflects the baseline level of disease normally found in that area. Lastly, an outbreak typically indicates a sudden rise in cases in a limited geographic area, which may lead to an epidemic if not controlled but still does not encompass the broader scope synonymous with a pandemic.