If the incidence of HBV is 30 cases in 100 persons of high risk group, during duration of 6 months… according to the equation the prevalence should be 180..?
A. The prevalence rate equals the incidence rate times the average duration of the disease. For example, if the average duration of a disease is 3 years and its incidence rate is 10 per 1,000, then the prevalence rate would be 30 per 1,000. The duration of disease is usually measured from the time of diagnosis to death (because time of onset of disease is usually difficult if not impossible). Incidence is usually calculated as yearly incidence and here you put an imaginary number and it is calculated per 1,000 so that’s why it looked wrong.
