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Chapter 9

Epidemiological Applications

P. deGravelles, PhD, RN

Objectives

1. Define epidemiology and describe how it has developed over time.
2. Describe the essential elements of epidemiology and an epidemiologic approach.
3. Discuss the steps in the epidemiologic process.
4. Explain the basic epidemiologic concepts of population at risk, natural history of disease, levels of prevention, host-agent-environment relationships, and the web of causation model.
5. Differentiate between descriptive and analytic epidemiology.
6. Explain how nurses use epidemiology in community health practice.

Define epidemiology and describe how it has developed over time. Obj 1

Epidemiology The study of the distribution and factors that determine health-related states or events in a population , and the use of this information to control health problems

History ■ 4th Century BCE: Hippocrates ■ 19th Century:

• Louis Pasteur– germ theory/pasteurization
• Joseph Lister– antiseptic surgery (Listerine)
• Robert Koch- discovered organisms of TB, anthrax, and cholera.
• (^) John Snow: FATHER OF EPIDEMIOLOGY (cholera outbreak)
• Florence Nightingale- environmental conditions of war ■ 20th Century:
• Shifted from looking for single agents to determining the multifactorial etiology
• Development of genetic and molecular techniques
• (^) New infectious diseases (HIV/AIDS, SARS)
• (^) Public health preparedness for bioterrorism

Elements of

epidemiology

Steps in the

epidemiologic

process

OBJ 3

1. A DIAGNOSTIC PHASE
   • (^) presence of the disease is confirmed. 2. A DESCRIPTIVE PHASE
   • (^) describes the populations at risk and the distribution of the disease, both in time and space, within these populations. This may then allow a series of hypotheses to be formed about the likely determinants of the disease and the effects of these on the frequency with which the disease occurs in the populations at risk.
2. AN INVESTIGATIVE PHASE
   • normally involves the implementation of a series of field studies designed to test these hypotheses.
3. AN EXPERIMENTAL PHASE
   • in which experiments are performed under controlled conditions to test these hypotheses in more detail, should the results of phase 3 prove promising.
4. AN ANALYTICAL PHASE
   • (^) results of the above investigations are analyzed. This is often combined with attempts to model the epidemiology of the disease using the information generated. Such a process often enables the epidemiologist to determine whether any vital bits of information about the disease process are missing.
5. AN INTERVENTION PHASE
   • (^) appropriate methods for the control of the disease are examined either under experimental conditions or in the field. Interventions in the disease process are effected by manipulating existing determinants or introducing new ones. 7. A DECISION-MAKING PHASE
   • explore the various options available for control of the disease. This often involves the modelling of the effects that these different options are likely to have on the incidence of the disease. These models can be combined with other models that examine the costs of the various control measures and compare them with the benefits, in terms of increased productivity, that these measures are likely to produce. The optimum control strategy can then be selected as a result of the expected decrease in disease incidence in the populations at risk. 8. A MONITORING PHASE
   • (^) takes place during the implementation of the control measures to ensure that these measures are being properly applied, are having the desired effect on reducing disease incidence, and that developments that are likely to jeopardize the success of the control program are quickly detected. http://www.fao.org/wairdocs/ilri/x5436e/x5436e06.htm

“POPULATION AT RISK” “NATURAL HISTORY OF DISEASE” “LEVELS OF PREVENTION” “HOST-AGENT-ENVIRONMENT RELATIONSHIPS” “WEB OF CAUSATION MODEL” OBJ 4

■ POPULATION AT RISK :

• “A^ certain portion of the population who is much more exposed to dangers or harm, in comparison to the larger population ”. ■ thelawdictionary.org/ population-at-risk / ■ NATURAL HISTORY OF A DISEASE:
• “the course of the disease process from onset to resolution ” ■ Porta et al., 2008 as found in Ch 9, Epidemiological Applications, Stanhope, M & Lancaster, J., (2014) p. 160

Differences between levels of prevention and Levels of care Levels of Prevention Levels of Care Primary Primary Level of Care That is our first - and most generalized - stop for symptoms that are new to us or concerns that we've contracted a cold, flu or other bacterial or viral disease. We may also seek out primary care for a broken bone, a sore muscle, a skin rash or any other acute medical problem we think we've developed. In addition, primary care should be our coordinating care, although that doesn't always happen the way it should. Primary care providers (PCPs) may be doctors, nurse practitioners or physician assistants. Secondary Secondary Level of Care Referral to a specialist by your PCP for whatever problem you are having. Secondary care is where most of us end up when we have a medical condition to deal with that can't be handled by primary care. For example, cardiologists focus on the heart and its pumping system. Endocrinologists focus on our hormone systems and some specialize in diseases like diabetes or thyroid disease. Oncologists work on cancers. Tertiary Tertiary Level of Care Referral system for the secondary care facilities. Provided complicated cases and intensive care. Medical centers, regional and provincial hospitals and specialized hospitals. 17

WEB OF CAUSATION