Which best describes a pandemic?

The term "pandemic" specifically refers to an epidemic that has spread across a large geographic area, typically affecting multiple countries or continents. This widespread transmission indicates that the disease is not confined to a specific location and has the potential to affect a substantial portion of the global population.

In contrast, a limited number of cases in a specific area would not qualify as a pandemic, as it lacks the extensive geographical spread. An outbreak across a wider geographical area might begin to approach the characteristics of a pandemic, but it is not definitive without the implication of extensive disease spread worldwide. Lastly, a single case of disease among travelers does not illustrate the scale or impact of a pandemic; rather, it is an isolated incident. Therefore, the best description for a pandemic is one that identifies it as an epidemic that has achieved a global reach.