3 Descriptive epidemiology which includes activities related to characterizing the di stribution of diseases within a population; Measures of disease occurrence—the tools for descripti ve epidemiology—were introduced in Epidemiologic Measures. In this chapter, these tools are used to characterize the p opulation distribution of tuberculosis. Toward that end, three basic questions can be asked: 1. Who develops disease? 2. Where does disease occur? 3. When does disease occur?
4 Collectively, these three questions serve as the basis f or a descriptive investigation of disease. Answers to these questions characterize the distributi on of tuberculosis by person, place, and time. As shown schematically in Figure 1, these features ar e the standard dimensions used to track the occurrenc e of a disease.
5 Person A basic tenet of epidemiology is that diseases do not occur at random. In other words, not all persons withi n a population are equally likely to develop a particul ar condition. Variation of occurrence in relation to personal charact eristics may reflect differences in level of exposure to causal factors, susceptibility to the effects of causal fa ctors, or both exposure and susceptibility. Typically, the minimal set of personal characteristics examined with respect to disease occurrence includes age, race, and gender.
6 Because such information is routinely collected on th e affected persons (cases), as well as the unaffected p opulation from which the cases develop, epidemiolog ists rely on these characteristics to a great extent. The use of other attributes of interest, such as level of education and income, marital status, and occupation , is contingent on the availability of data.
7 The number of reported cases of tuberculosis by age in the United States during 2002 is shown in Figure 2. It should be emphasized that these data are derived from information reported by physician s, laboratories, and other health care providers. Tuberculosis is on e of over 60 infectious diseases that currently are designated as no tifiable at the national level within the United States. The Centers for Disease Control and Prevention (CDC) define a notifiable dise ase as follows: A disease for which regular, frequent, and timely information on i ndividual cases is considered necessary for the prevention and co ntrol of the disease.
8 Reporting of notifiable diseases in the United States typically begi ns with a clinician forwarding basic information on a newly diagn osed patient to the designated local or state health department. On a weekly basis, state and territorial officials transmit informati on about individual or aggregated cases of nationally notifiable di seases to the CDC. These reports follow a standard format, includ ing information on the age, sex, and race of the patient, and date o f occurrence of reported cases.
9 Figure 2 appears that the age group with the highest risk of tub erculosis is 25–44 years. This conclusion is incorrect, however
- Spring '16