Define "pandemic."

A pandemic is defined as an epidemic that has spread over multiple countries or continents, affecting a large number of people. This definition emphasizes the extensive geographic reach and the significant impact on populations, distinguishing it from a localized outbreak or epidemic that may occur in a specific region.

For example, the COVID-19 pandemic demonstrated how a novel virus can quickly transition from an outbreak in one location to a global crisis, illustrating the characteristics of a pandemic: widespread transmission, high infection rates, and a significant burden on health systems across different nations.

The other choices do not align with the accepted definition of a pandemic. A sudden outbreak in a small area refers to a localized incident and does not capture the large-scale aspect of a pandemic. A local health initiative is unrelated to disease spread and pertains to efforts to improve health within a specific community. A short-term disease outbreak also falls short of describing the global implications and prolonged nature often seen with pandemics. Thus, the correct understanding of a pandemic lies in its broad and far-reaching effects on health across different regions.