Chetan epidemiology

SEMINAR ON

EPIDEMIOLOGYPRESENTED BY MR. CHETAN AMBUPEFINAL YEAR M.SC (N)

DEFINITIONS

• The epidemiology is that branch of medical science which deals with epidemics (Parkin, 1873).

• Epidemiology is the science of mass phenomena of infectious diseases (Frost, 1927).

• Epidemiology is the study of disease, any disease, as a mass phenomenon (Greenwood, 1934).

• Epidemiology is the study of the frequency, distributions and determinants of health related states or events in specified population and the application of this study to control health problems (Last, 1988).

PURPOSES

• To prevent, control and eradicate health and health related problems.

• To reduce/minimize the impact of these problems.

• To promote health and quality of life of people at large.

OBJECTIVES OF EPIDEMIOLOGY

• Study of frequency and distribution of health and health related problems in community at large.

• Identification of determinants i.e. etiological factors causing health and health related problems.

• Need based planning and administration of comprehensive health care programmes with the available resources to deal with health and health related problems.

• Evaluating the effectiveness of the programmes to provide feedback.

USES OF EPIDEMIOLOGY

Study the occurrence and distribution of diseases in a community.

Identify the determinants of diseases.

Diagnose the health status of the community

Estimate the risk

Plan effective need based health care services

Determine the effectiveness of health care services planned.

Determine the usefulness and effectiveness of new/innovative techniques, measures and programmes

Complete the clinical picture of chronic diseases arid slow growing diseases

Identify syndromes by describing the distribution and association of clinical phenomena in the population.

Forecast the likely occurrence of diseases on the basis of epidemiological principles

THEORIES AND MODELS OF DISEASE CAUSATION

Supernatural theory

The Germ Theory

Theory of Epidemiological Triad

Multifactorial Causation Theory

Web of Causation

Dever’s Epidemiologic Model

EPIDEMIOLOGICAL METHODS

OBSERVATIONAL STUDIES Descriptive studies Analytical studies EXPERIMENTAL STUDIES Randomized control trials Field trials Community trials

Descriptive Method

Descriptive method of epidemiological study is concerned with the study of frequency and distribution of disease and health related events in population in terms of person, place and time.

Personal characteristics such as age, sex, race, marital status, occupation, education, income, social class, jury pattern, habits.

Place distribution of cases i.e. areas of high concentration, low concentration and spotting of cases

Time distribution/trends such as year, season, month, week, day and hour of onset of the disease

There are two different designs to conduct descriptive studies in epidemiology:

1) Cross-sectional studies:

2) Longitudinal Studies:

USES OF DESCRIPTIVE EPIDEMIOLOGY

Provide data regarding the magnitude of the disease load & types of disease problems in the community in terms of morbidity & mortality rates & ratios.

Provide clues to disease etiology & help in the formulation of an etiological hypothesis.

Provide back ground data for planning, organizing , & evaluating preventive & curative services.

Contribute to research by describing variation in disease occurrence.

Procedures in descriptive studies

Define the population to be studied

Defines the disease

Describe the disease

Time, place and person

Measurement of disease

Comparing with known indices

Formulation of hypothesis.

ANALYTICAL EPIDEMIOLOGY

The object is not to formulate hypothesis but to test hypothesis.

It contains two types: CASE CONTROL STUDY COHORT STUDY

CASE CONTROL STUDY {RETROSPECTIVE STUDIES}

HAS 3 DISTINCT FEATURES:• Both exposure & outcome has occurred

before the onset of study

• Study proceeds backwards from effect to cause

• It uses a control or comparison group to support or repute an inference.

There are four basic steps in conducting a case control study:

1. Selection of cases and controls

2. Matching

3. Measurement of exposure, and

4. Analysis and interpretation.

COHORT STUDY

FEATURES ARE:• Cohorts are identified prior to the

appearance of disease under investigation.

• Study groups are observed for a period of time to determine the frequency of disease among them.

• Study proceeds forward from cause to effect.

ELEMENTS OF A COHORT STUDY

1. Selection of study subjects

2. Obtaining data on exposure

3. Selection of comparison groups

4. Follow – up, and

5. Analysis.

Experimental Method

Experimental studies are similar in approach to cohort studies except that conditions are under the careful control of investigator

Experimental studies are of two types:

a. Randomized controlled trials; and

b. Non-randomized or “non-experimental” trials

EPIDEMIOLOGICAL MEASUREMENTS

1.Mortality Rate (Death Rate)

2. Morbidity Rates -

EPIDEMIOLOGICAL APPROACHES

1. Asking questions and making observations.

2. Making comparisons.

PREVENTIVE EPIDEMIOLOGY

Health surveys

Health surveys are investigations to identify the frequency, distribution and the determinants of health related events or states in the community. Health surveys help in knowing the community and making community diagnosis.

i) Questioning

ii) Health examination and lab. Investigations

iii) Record review

iv) Observation

SCREENING

Screening form health point of view is defined as the method of search for unrecognized diseases by means of rapidly applied tests, examinations or procedures in apparently healthy population.

Mass Screening:

Multiphase Screening:

Selective or High Risk Screening :

SURVEILLANCE

Epidemiologically surveillance means close vigilance on occurrence and distribution of diseases and health related problems, population dynamics, community behavior and environmental processes resulting in increased risk of ill health in the community.

Individual/Family Surveillance:

Community/Local Population Surveillance

National surveillance:

International surveillance:

MONITORING

Monitoring is day to day measuring and analysis i.e making assessment of: health status of people and their environment to determine any changes; ‘performance of health services and health professional to determine effectiveness and efficiency; health behavior of client to determine compliance of behavior.

DYNAMICS OF DISEASE TRANSMISSION:

1. The Reservoir.

2. Mode of Transmission.

3. Susceptible Host.

Reservoir of infectious agent: In simple terms, reservoir means the

natural habitat. The reservoir of infectious agent is any person, animal, arthropod, Plant, soil and any substance.

Types of Reservoir

1. Homologous Reservoir

2. Heterogonous Reservoir

HUMAN RESERVOIR The human is the source of infection

and act as a host for infectious agent. Human itself is responsible for spreading many diseases in humans either by suffering and carrying the infectious agent

HUMAN RESERVOIR IS OF TWO TYPES

1. Cases

The cases are of following types:

Clinical cases

Sub clinical cases

Latent cases

2. CARRIERS:

MODES OF TRANSMISSION

DIRECT TRANSMISSION• Direct contact

• Droplet infection

• Contact with soil

• Inoculation into skin or mucosa

• Trans placental or vertical transmission

INDIRECT TRANSMISSION

• Vehicle borne

• Vector borne

• Air borne

• Fomite borne

• Unclean hands & fingers

SUSCEPTIBLE ‘HOST

The infectious agent enters the susceptible host after finding a portal of entry such as respiratory tract, alimentary tract, skin etc. Inside the human host, on getting appropriate environment, it multiplies and sufficient density of the disease agent is built up to disturb the health equilibrium and the disease become overt.

LEVELS OF PREVENTION

PRIMARY PREVENTION

SECONDARY PREVENTION

TERTIARY PREVENTION

IMPLICATIONS OF EPIDEMIOLOGY IN C.H.N PRACTICE

An understanding of epidemiological concepts & principles are vital for nurses in the community as well as hospital setting.

Knowledge of methods of epidemiology is useful to the C.H. nurse, both as tool in conducting the investigation to evaluate & explain phenomena observed in the course of work & as a basis for interpreting & evaluating the epidemiological literature.

Epidemiological methods such as measures of health , serve as tools for assessing community needs & evaluating the impact of C.H. programmes of disease prevention & health promotion.

The body of knowledge derived from epidemiological studies , including the natural history & patterns of disease occurrence & factors associated with high risk for developing disease, serves as an information base for C.H. practice .

It provides a frame work for planning,& evaluating community intervention programmes.

Serves as a basis for assessing individual & family health needs & for planning nursing interventions.

Provides tools for evaluating success of interventions.

Nurses may be the one who initiate a study & more frequently assist in data collection.

In actual practice, C.H. nurse is considered as the foot soldier in the army of epidemiology.

Epidemiologist depend on C.H. nurse for follow- up on various conditions.

ROLE OF NURSE IN EPIDEMIOLOGY:-

She makes use of nursing process which is comparable to epidemiological process in solving the problem.

She identifies & investigating the problem, formulates interventions & implements to prevent & control the problem & evaluate the effectiveness of intervention.

She deals with the problem independently especially when these are nursing problem, minor ailments.

She may participate as one of the team members.

She participates in data collection, data analysis, planning, implementation & evaluation.

She play active role in prevention & control of communicable diseases.

Community health nurse can also teach & supervise other workers in surveillance activities.

She also participates in National programs.

Conclusion:-

Epidemiology is one of the basic sciences applicable to nursing. Nurses working in the community deal with the people in various settings and help them to solve their health problems. Nurses in the community have an active role in prevention and control of communicable diseases