Which term is used to describe a disease that affects large numbers of individuals in a population?

The term "epidemic" is used to describe a disease that affects large numbers of individuals within a specific population or geographic area within a certain period of time. This term indicates a sudden increase in the number of cases of a disease above what is normally expected in that population. Epidemics can arise due to various factors such as the spread of infectious diseases, changes in environmental conditions, or the emergence of new pathogens.

While a virus is a type of pathogen that can cause diseases, it doesn’t refer specifically to the scale of disease occurrence within a population. Epidemiology is the study of how diseases spread and are controlled within populations, but it does not describe a specific outbreak. The term "plague" typically refers to specific infectious diseases, most commonly associated with Yersinia pestis, and while it can cause significant epidemics, it is not a general term for any disease affecting large numbers. Therefore, epidemic is the most accurate term to describe widespread disease occurrences in a population.