Epidemiology - Basic Epidemiology
1. What is Epidemiology?
Prevalence of DiseaseThe prevalence of a disease is a measure of number of cases within the population at a defined time and the incidence is a measure of the number of new cases arising within the population in a given time period. Common colds may be seen to have low prevalence and high incidence in a population as they occur frequently but only last a short time (i.e. have short duration). Diseases such as asbestosis have low incidence (i.e. new cases occur relatively rarely) but as the disease is permanent (i.e. of long duration) have high prevalence. Prevalence and incidence are measured by counting the number of cases in a defined population at risk. This data is most usefully presented as rate values as discussed later in this chapter.
The knowledge of disease burden within a population can enable targeting of resources to achieve maximum benefit for the health status of that population. Epidemiology can provide information on both the prevalence of disease at a specific time and its incidence over a period of time. This is illustrated in Figure 3:
Figure 3 Health Status
Epidemiological tools can be used to measure the effectiveness of interventions designed to reduce ill health and disease. This is illustrated in Figure 5.4 below:
Figure 5.4 Evaluation of Intervention