Final answer:
An epidemic is a term used when the prevalence of a disease sharply increases in a short period of time. Examples include influenza outbreaks and emerging diseases like Ebola and Zika viruses.
Step-by-step explanation:
An epidemic is the term used when the prevalence of a disease is increasing beyond what is expected in a short period of time. Epidemic diseases are characterized by a larger than expected number of cases occurring in a short time within a specific geographic region. Examples of epidemic diseases include influenza outbreaks that occur during winter seasons. Additionally, emerging and re-emerging diseases are infectious diseases that have substantially increased or threaten to increase in the near future. These diseases include Ebola virus, West Nile virus, Zika virus, SARS, H1N1 influenza, and HIV, among others.