Incidence and Prevalence
Incidence is the number of cases of a disease that are diagnosed for the first time during a given period of time. For example, over the past four years, the incidence of MRSA, a staph infection that is resistant to antibiotics, has been on the rise. Incidence is different from prevalence, which is the total number of people affected by a disease or condition at a particular point in time. For example, school administrators are concerned that attention-deficit disorders (ADD and ADHD) have become more prevalent.