Question

Q2: (a) The prevalence of a disease in a population is 0.02. Explain the meaning of this in your own words. (1pt) (b) The incidence rate of a disease in a population is 5 per 10,000 person years. Explain the meaning of this in your own words. (1pt)

Answer 1

Prevalence measures how much of some disease or condition there is in a population at a particular point in time. Prevalence is a frequently used epidemiological measure of how commonly a disease or condition occurs in a population. The prevalence is calculated by dividing the number of persons with the disease or condition at a particular time point by the number of individuals examined. It can refers to the number of cases of a disease that are present in a particular population at a particular point of time. Thus,

Prevalence of Disease = P/P, where p = number of cases, and P is the population size at a given time, t.

Therefore, if 100 is the population size and the number of disease cases is 2, then the prevalence = 2/ 100 = 0.02.

It shows that prevalence is measured in an open population and all cases (new and old) of disease are counted as the number of cases.

Incidence rate of a disease is a statistical calculation that calculates the proportion of the number of disease onsets and total population at the risk time. It can be written as

Incidence rate, IR = (number of disease onsets) / (sum of person - time at risk).

It is the number of new cases per population at the given time of period. It is the rate of occurrence of new disease and thus differs from the prevalence of disease. In a population is 5 per 10,000 person years incidence rate of a disease is 5*10^-4.