Which definition best describes a 'pandemic'?

The definition that best describes a 'pandemic' is a high number of disease cases across various regions. A pandemic typically refers to an outbreak of a disease that occurs on a global scale, affecting a large number of people in multiple countries or continents. This widespread occurrence distinguishes a pandemic from other types of disease outbreaks, such as epidemics, which are more localized.

The concept of a pandemic encompasses the idea of not just a high incidence of cases, but also the severe impact it can have on public health systems and societies at large. It indicates not just the spread of a disease, but also the potential for widespread contagion and the need for coordinated public health responses across different jurisdictions.

The other options relate to different concepts: a dramatic increase in a condition within a community describes an epidemic; programmed cell death (apoptosis) refers to a biological process at the cellular level; and excessive fluid in body tissues pertains to edema, which is a medical condition but not related to the definition of pandemic. Understanding these distinctions helps clarify the unique nature of pandemics in the context of global health.