Final answer:
Endemics are diseases that are constantly present in a population, epidemics occur when there is an unusual rise in the number of cases, and pandemics are epidemics that spread on a global scale.
Step-by-step explanation:
Epidemiologists play a crucial role in understanding and managing diseases within populations. When we talk about diseases in terms of their spread and prevalence, we use terms like endemic, epidemic, and pandemic.
An endemic disease is one that is constantly present in a population, usually at a low but stable incidence. It's something that is regularly found within a certain area or among a particular group of people. For example, malaria is endemic in certain parts of the world.
An epidemic disease is one that sees an unusual spike in the number of cases in a population at a given time. It's a disease outbreak that exceeds what is expected based on recent history. Seasonal flu can often rise to an epidemic level in a population during specific times of the year.
When an epidemic spreads over larger geographic areas and affects a significant portion of the population, it becomes a pandemic. This term is used when the spread of disease is not just localized, but occurs on a global scale. An example of a pandemic is the outbreak of HIV/AIDS.