Download - Investigation Epidemic

8/7/2019 Investigation Epidemic

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INVESTIGATION OF AN EPIDEMIC


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VERIFICATIONS OF DIAGNOSIS

It is the first step ,do as quickly as possible. It is not

necessary to examine all the cases to arrive at a

diagnosis. clinical examination of a sample of cases

may well suffice. Lab investigations are most usefulto confirm the diagnosis but the epidemiological

investigations should not be delayed until the lab

results are available


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CONFIRMATION OF THE EXISTENCE

OF AN EPIDEMIC

Second step. Done by comparing the disease

frequencies during the same period of previous

years. An epidemic is said to be exist when the no.

of cases is in excess of the expected frequency forthat population based on past experience


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DEFINING THE POPULATION AT RISK

A.Obtainig a map of the area.

Before beginning the investigation it is necessary to havea detailed and current map of the area. It shouldcontain information concerning natural landmarks, roadsand location of all dwelling units in each road or inisolated areas. Area may be divided into segments,using natural landmarks as boundaries. This may againdivided into smaller sections. Within each section thedwelling units may be designated by numbers.

B.Counting of the population

A complete census of the population by age and sex byhouse to house visits(if the general population affected)


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RAPID SEARCH FOR ALL CASES AND

THEIR CHARECTERISTICS

B.Epidemiological case sheet

This includes:

Name,Age,Sex,Occupation,Socialclass,Travell,

History of previous expossure,Time of onset ofdisease,Signs&Symptoms of illness,Personnel contact athome,work,school and other places,Special events suchas parties attended, Foods eaten, and exposure to

common vehicles such as water, food and milk, visits outof the community, History of injections, or bloodproducts, attendance at large gatherings. If the outbreak is large-random sample.


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RAPID SEARCH FOR ALL CASES AND

THEIR CHARECTERISTICS

C.Searching for more cases:

Patient may be asked if he knew of other cases inthe home,family,neigbourhood,school,workplace,

having an onset within the incubation period ofthe index case, cases admitted to local hospitalsshould also be taken into consideration. Searchshould be carried out every day till the area is

declared free of epidemic. This period is usuallytaken as twice the incubation period of the diseasesince the occurrence of last case


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DATA ANALYSIS

A . Prepare a

chronologicaldistribution ofdates of onsetand construct

an epidemiccurve


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DATA ANALYSIS

B. Place

prepare a spot map of cases(geographic distribution)

and if possible their relation to possible sources of

infection eg:water supply, air pollution, foods eaten,

occupation etc.Clustering of cases may indicate a

common source of infection


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DATA ANALYSIS

C.Person

Analyze the data by age,sex,occupation and other

possible risk factors. Determine the attack rate/

case fatality rate


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FORMULATION HYPOTHESES

On the basis of time-place-person/agent-host-

environment model, formulate hypotheses to explain

the epidemic in terms of

A. Possible source

B. Causative agent

C. Possible mode of spread and

D. The environmental factors which enabled it to occur


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TESTING OF HYPOTHESES

All possible hypotheses need to be considered and

weighed by comparing the attack rates in various

groups for those exposed, those not exposed to

each suspected factor


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EVALUATION OF ECOLOGICAL

FACTORS

Evaluation of the circumstances involved should be

carried out to undertake appropriate measures to

prevent further transmission

Sanitary status of eating establishments, water and

milk supply, breakdown in the water supply system,

movements of the human population, atmospheric

changes such as temp.,humidity and air pollution,population dynamics of insects, and animal reservoir

Source-reservoir-modes of transmission


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FURTHER INVESTIGATION OF

POPULATION AT RISK

Medical examination, Screening tests, examination of

suspected food,faeces or blood samples,

biochemical studies,assesment of immunity status


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The report should be complete and

convincing.

WRITING THE REPORTS


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CONTENTS OF REPORT

1. Back ground

2. Historical data

3.

Methodology of investigation4. Analysis of data (clinical data,Epideiological

data, modes of transmission, Lab data,

Interpretation of data)

5. Control measures

6. Evaluation

7. Preventive measures


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BACK GROUND

Geographical location

Climatic conditions

Demographic status(Population pyramid) Socio-economic situation

Organization of health services

Surveillance&early warning systems

Normal disease prevalence


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HISTORICAL DATA

Previous occurrence of epidemics

1.Of the same disease

2.Locally or elsewhereOccurrence of related diseases if any

In the given area

In other area

Discovery of first case of the present outbreak.


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METHODOLOGY OF INVESTIGATION

Case definition,

Questionnaire used in epidemiological investigation

Survey teamsa. House to house

b. Retrospective

c. Prospective

Collection of Lab. Specimens

Lab techniques


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ANALYSIS OF DATA

A. Clinical data

1.Frequency of signs&symptoms

2. Course of disease

3. Different diagnosis

4. Death or sequelae rates

B.Epidemiological data

1.Mode of occurrence2. In time

3.By place

4. By population groups


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ANALYSIS OF DATA

C. Modes of transmission

1. Source of infection

2.

Route of excretion and portal of entry3. Factors influencing transmission

D. Lab data

1. Isolation of agents

2. Serological confirmation

3. Significance of results


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ANALYSIS OF DATA

E. Interpretation of data

1. Comprehensive picture of the outbreak

2.

Hypotheses on causes3. Formation and testing hypotheses by statistical

analysis


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CONTROL MEASURES

Definitions of strategies and methodology of

implementation

Constraints

Results


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EVALUATION

Significance of results

Cost/Effectiveness

Preventive measures


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THANK YOU

SUGUNAN.KR

HEALTH INSPECTOR

PHC PINDIMANA&PUNNEKKAD

MOB:9446024671