incidence and prevalence

Incidence and prevalence are two ways to measure how common a disease is. Incidence refers to the number of new cases that develop in a specific population during a certain time period, indicating how quickly a disease is spreading. Prevalence, on the other hand, counts all existing cases—new and old—at a particular point or over a period, showing how widespread the disease is at that time. In essence, incidence measures new occurrences, while prevalence reflects the total burden of disease in a community.