Field and Uses of Epidemiology and Epidemiological Approaches

Field of Epidemiology

Epidemiology includes all major community diseases, infectious diseases, chronic degenerative disorders, metabolic processes, nutritional deficiencies, injuries, social, psychological and behavioral disorders and the other population problems. Epidemiologic methods range from a simple observation and description to analytical methods designed to identify the cause and effect relationships. epidemiology today is very broad and focuses on many directions.

Geographic epidemiology

One of the epidemiological approaches is to compare the incidence/prevalence and characteristics of a disease in different places. Previous works in geographic epidemiology concerned mainly with diseases in relation to the physical features of the environmental factors. Travel has made the health problems of individual country to be the problem of the world e.g. HIV/AIDS, making concern for the geography of disease at national and international levels. Nowadays, advanced statistical and mapping softwares such as GIS have been developed to measure the spatial distribution of disease.

Social epidemiology

The study of social conditions and their influence on determination of the health situation of populations is called social epidemiology. IN recent years, a stronger tie between epidemiology and the social sciences has been evolved. Social epidemiology has been promoted by the need to recognize and document the wide spectrum of health determinants, from a micro level where individual biological factors operate, to a macro level that expresses social conditions in which populations live. The principal concern of social epidemiology is the study of how society and different forms os social organizations influence the health and well-being of individuals and populations. In particular, it studies the frequency, distribution, and social determinants of the states of health in a population. Thus, social epidemiology goes beyond the analysis of individual risk factors to include the study of the social context in which the health-disease phenomena occurs.

Clinical epidemiology

Proper identification of disease or injury in individual is essential to have study of manifestation in agroup. For this, clinical understanding is the basic. Epidemiological studies have been extended from epidemic to sporadic and isolated foci of infection, to patient's behavior in relation to his family, his environment, and close associates. Clinical epidemiology is often complemented by laboratory procedures.

Statistical epidemiology

All epidemiologic procedures involve mathematics, from research design phase to analysis phase, from simple arithmetic to advanced statistical methods to establish a relationship between dependent and independent variables, and to interpret the results.

Statistical methods are the main epidemiologic tools and applicable to data from almost all sources. Statistical methodsoften concern with frequency, rate of occurrence according to time, place and person, and changes in characteristics of disease. It helps to build up and confirm theoretical concept through statistical models arising from experiments or observations.

Descriptive epidemiology and Field survey

Descriptive epidemiology and field survey are cross-sectional studies and look for the number of cases of disease, or of aperson with some attributes. It is a prevalence study, and it is a way to determine point prevalence or prevalence at a specified time period.

Descriptive studies and field surveys can use clinical, and laboratory approach or field investigation using questionnaires or combination of all three. The field surveys often help to find causation of disease. These are often of short duration but may be repeated at interval to determine period prevalence and to increase the potentiality to determine causative factors.

Analytical epidemiology

prospective study concerns with incidence rather than prevalence. Retrospective and prospective studies aim to establish causal relationship. In analytical study, data are collected according to a carefully formed plan, with condition defined, constants established, and control provided.

Experimental epidemiology

Experimental epidemiology attempts to explore principles of disease occurrence, prevention and control by direct experimentation with subgroup of population having control. Experimental epidemiology is a method of proving or disproving a hypothesis.

Infectious disease epidemiology

Operational epidemiological studies in communicable disease control purposes to identify sources of infection for developing proper control measures, and preventive practices to avoid the subsequent outbreak. House to house screening is done and further information collection is done by observational and descriptive methods. In case of epidemics, identification of the immediate sources of infections is important for institution of proper control measures. Further, identification of reservoir of infection increases the chances of avoiding future epidemics.

Uses of Epidemiology

Epidemiology is used in anumber of ways. In earlier days, epidemiology was concerned with the causes of communicable diseases. Epidemiology is the basic medical science with the goal of improving the health of populations. It is increasingly used to study genetic and environmental factors influence in human and preventive intervention through health promotion. Epidemiology also concerns with natural history of disease in individual and groups. Recently, its area is broadened and used in theevaluation of the effectiveness and efficiency of health services and health programs. Briefly, epidemiology is used for followings:

1. Investigation of causation of disease

2. Study of natural history and prognosis of the disease

3. Description of health status of population (proportion of ill health, changes of disease pattern over time, age, peography etc.)

4. Evaluation of interventions (preventive and therapeutic0 and health programs

5. Planning health services, public policy and programs

6. To study the working of health services, determination of needs and resources, proceed for analysis of services in action.

Epidemiological Approaches

There are three major epidemiological approaches:

Descriptive epidemiology

Descriptive epidemiology is the frequent method to determine incidence, prevalence and mortality rates in the population. These indicators are classified by sex, age, race, ethnic group, occupation, education, social class, geographic location and time. Mainly, it concerns with the following characteristics:

1. Types of disease or health problem
2. Person (WHO)
3. Place (WHERE)
4. Time (WHEN)

The approach in descriptive epidemiology is to ask questions related to health events or related to health sciences.

Questions related to health events:

• What disease or health problems occurred in the community?
• Who were the people affected?
• Where did the disease occur?
• When did the disease occur?
• Why did it happen?
• How did it happen?

Questions related to health actions:

• What can be done to reduce these problems and its consequences?
• How can it be prevented in the future?
• What action should be taken by the community or by the health services?
• What resources are required?
• What difficulties may arise and how might they be overcome?

Descriptive epidemiology provides ground for planning and evaluations of health care facilities by characterizing disease or health problems in population. Based on all these information, effective disease prevention and control strategies can be developed.

Analytical Epidemiology

Analytical epidemiology implies the use of studies to test a hypothesis. It involves evaluation of determinants of disease distribution in term of possible causal factors. There are basically two approaches,case-control and cohort studies. Analytical epidemiology is the crucial part of epidemiology since it provides the scientific basis for the causal relationship of the disease. Descriptive epidemiology usually involves the total characterization of a disease, and generation of etiologic hypothesis whereas analytical epidemiology require more special studies to answer a specific question or to test a hypothesis.

Operational and Experimental epidemiology

The field activities that constitute operational epidemiology are:

• Investigation of disease outbreak
• Implementation research in different health problems or diseases
• Administrative prevention and control of disease or health problems.

Their main function is to support the practical work of public health sectors:

Experimental epidemiology includes:

1. Randomized controlled trials
2. Non-randomized controlled trials
3. Quasi-experiments

In summary, epidemiology can be classified in the following components. Serological, molecular and clinical epidemiology can be included within other three mentioned componenets or can be considered separate because of specific methods used to determine the health problems.

1. Descriptive epidemiology
2. Analytical epidemiology
3. Serological epidemiology- Immunological studies and Clinical studies
4. Clinical epidemiology
5. Molecular epidemiology

Differences between Clinical Medicine and Epidemiology

The following are the differences between epidemiology and clinical medicine:

Comparison between epidemiology and clinical medicine

Equivalence of clinical procedure with community diagnosis

Reference

Atlas, RM and R Bartha. Microbial Ecology:Fundamentals and Applications. The Benjamin Cummins Publication co. Inc., 1998.

Gordis, L. Epidemiology. third edition. 2004.

Maier, RM, IL Pepper and CP Gerba. Environmental Microbiology. Academic press Elsevier Publication, 2006.

Park, K. Park's Text Book of social and prevention Medicine. 18th edition. 2008.