ABSTRACT
Incidence o The rate at which new cases occur within a given period of time, o = number of new cases/(population at risk x time period), o E.g. in a school with 1,000 pupils, there were 5 new cases of meningitis
in the 6-month period between 1/1/2003 and 1/7/2003). Incidence = 5/(1,000 x 0.5) = 1 per 100 person-years at risk. Prevalence
o Point prevalence - the proportion of a population who have the disease at any one point in time.
