Question

An unusual infectious disease has affected a small community (population = 962 persons) and infected 123 people over a one-year period. Further, 17 infected persons have died in that year. Alarmed by the first year’s experience, the local Public Health Department set up a cohort study at the start of the second year, and followed the remaining healthy members of the population annually for the next three years. At the end of the first year of the cohort study, 97 more cases were detected. At the end of the second year, 73 more cases were detected and 16 people were lost to follow-up. At the end of the third year, an additional 52 cases were detected, and 13 more were lost to follow-up.
What was the incidence proportion, or cumulative incidence, of the disease over the three-year cohort study, calculated as a proportion to one decimal place?
What was the incidence rate over the three years of the cohort study, expressed as cases per 1,000 person-years and calculated to one decimal place?

Answer 1