Final answer:
The Centers for Disease Control and Prevention (CDC) classifies diseases as epidemic when they affect many individuals in a population simultaneously, pandemic when the epidemic spreads on a global scale, and endemic when the disease is consistently present at a stable rate within a population.
Step-by-step explanation:
The Centers for Disease Control and Prevention (CDC) may announce a disease status based on its spread and persistence in the population. An epidemic refers to a disease that occurs in an unusually high number of individuals in a population at the same time. When an epidemic spreads over multiple countries or continents, it becomes a pandemic. In contrast, an endemic disease is one that is consistently present in a population, typically at low frequencies. Lastly, a disease's contagious nature indicates how easily it can spread from person-to-person, which is not specific to the disease's status in terms of being epidemic, pandemic, or endemic.
For instance, the flu (influenza) often reaches epidemic levels during a particular season, while diseases such as HIV/AIDS have reached pandemic levels. Endemic diseases may include ailments like the common cold, which are continuously present within a particular region.