Epidemiology's Role in Public Health

We talked briefly about the two aspects of Epidemiology: descriptive and analytical. Epidemiologists use both of these methods in public health practice. Public health is the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals. Also, public health activities use epidemiological principles and methods. Examples of these activities include surveillance, disease investigation, community health assessment, screening, targeting intervention programs, and evaluation of intervention programs.

Surveillance

The Centers for Disease Control and Prevention, or CDC, defines this activity as follows: public health surveillance is the ongoing, systematic collection, analysis, interpretation, and dissemination of information or data about a health-related event to those who need to know so that action may be taken to reduce morbidity and mortality and to improve the public's health. Public health surveillance involves: collecting health information routinely, examining or analyzing that information, and communicating your conclusions about the information to the public and others.

Surveillance data are used by a variety of individuals and organizations for health promotion and disease prevention purposes, and many types of surveillance systems exist to collect these data. On the state level, there are surveillance systems that start with a state-specific official list of reportable diseases. These systems use passive surveillance, in which cases or data are reported by health care providers and laboratories either to local health jurisdictions or directly to the state health agency. For some reportable diseases or conditions active surveillance may be used instead. In active surveillance state or local public health personnel actively reach out to providers and laboratories, making periodic personal visits or phone calls asking about the recent occurrence of the disease or condition under surveillance. Active surveillance may be used also under special conditions such as community or school outbreaks.

Disease Investigation

Disease investigation is a core epidemiologic function in public health, and it is most often used in situations of short-term outbreaks of infectious diseases such as those associated with food or environmental contamination. The first goal of a disease outbreak investigation is to identify the source of the illness of which there is an apparent outbreak or sharp increase in occurrence. This information will help you develop and implement the appropriate intervention to control the outbreak as well as develop prevention policies necessary to protect the public's health. Outbreaks can be recognized through several mechanisms, including analysis of routinely submitted notifiable disease surveillance data or through reports from health care providers, from clinical laboratories, or from the individuals who are themselves affected by the illness in question. An early step is often to describe the outbreak in descriptive terms: Who is affected, where are they, and when did they become ill? Next the investigation seeks to identify the determinants of the outbreak by using analytic epidemiologic methods, including conducting analytic studies and calculating disease rates or risk associated with specific foods, behaviors, and other factors.

Assessment

Assessment is one of the three core public health functions. In public health, assessment refers to a process that provides pertinent information to assess the health of a community. When doing community health assessment, descriptive epidemiology tools are used to answer questions. The information is often noted in terms of age, gender, race distribution, the amount of new cases of health related events. Knowing what information to gather and how to interpret it requires local and regional knowledge of the community. The goal of a community health assessment is to provide a product to share with the public and with local policy makers.

Screening

Screening is another aspect of public health practice that involves the use of epidemiology. The classic definition of screening is the examination of asymptomatic people in order to classify them as likely, or unlikely, to have the disease that is the object of screening. This is not the same as diagnosis, that is, you are not saying they do or do not have the disease, just that it is likely or unlikely that they do. Epidemiologists measure both the accuracy of screening tests and the effectiveness of screening programs.

Intervention Programs

After determinants of diseases or health events are identified through descriptive and analytic epidemiologic studies, public health interventions are developed targeting the segment of the population found to be most at risk for the problem. The choice of the target group and the intervention are based on the public health assessment of the specific condition. Interventions are targeted to make the best use of public health resources to gain the greatest effect as measured by health outcomes. For example, to use a targeted intervention approach for SIDS prevention you might identify which groups within your population are at higher risk of SIDS. Or if you are focusing specifically on a sleep position intervention, you could identify groups who might be more likely to place their infants in the prone position for sleep—such as older women who have other children and may have established their infant care patterns at an earlier time. Then you would develop interventions such as educational programs likely to reach those groups.

Program Evaluation

Public health program evaluation is a systematic way to collect information about the characteristics, activities, and results of a program in order to make decisions about the program. In other words, you use evaluation to gather evidence to determine the value of a program—is it worthwhile, useful, important? Program evaluation helps you to answer the key question: Is this program making a difference? You can use evaluations to document a programs progress and to measure its effectiveness.

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