An epidemic is a sudden increase in the number of cases of a disease within a specific geographic area or population. It occurs when a new strain of a virus or bacteria spreads rapidly, affecting a larger number of people than usual. Epidemics can be caused by various factors, including environmental changes, increased human interaction, or the emergence of new pathogens. Epidemics can impact public health systems and require coordinated responses to control the spread of the disease. Measures may include vaccination campaigns, public awareness programs, and quarantine protocols. Examples of epidemics include the H1N1 influenza outbreak and the Ebola virus epidemic.