What term describes a very large increase worldwide?

The term that describes a very large increase worldwide is "pandemic." A pandemic refers specifically to the spread of a disease across multiple countries or continents, affecting a large number of people. It indicates a global health crisis where the infection can spread significantly, transcending geographic and political boundaries.

In the context of infectious diseases, a pandemic highlights the scope and severity of the outbreak, often requiring international attention and collaboration to manage effectively. The significance of the term is underscored by recent events, where terms like "pandemic" have become familiar in discussions about global health challenges.

While the other terms listed relate to the spread of diseases as well, they describe different scenarios. An epidemic is typically confined to a specific region and can imply a sudden increase in cases within that area. Endemic refers to diseases that are consistently present in a particular geographic area, maintaining a stable presence over time. An outbreak, while also indicating a rise in cases, usually refers to a localized increase rather than a global phenomenon. Therefore, "pandemic" is the appropriate choice for a very large worldwide increase.