Management of an epidemic

MANAGEMENT OF AN EPIDEMIC

By – Dr. Dharmendra Gahwai

Definition

Epidemic is defined as – “ the unusual occurrence of the disease or health related event in a community or region, clearly in excess of “expected occurrence”.

The term “outbreak” is used for a small usually localized epidemic.

The severity of epidemic depends on – 1. Environmental condition.

2. Characteristic of host population.

3. Socio-cultural behavior of people.

TYPES OF EPIDEMICS

1. Common Source Epidemics. (a).Point source or Single exposure (b).Continuous or Multiple exposure.

2. Propagated Epidemics (a). Person to person. (b). Arthropod vector. (c). Animal Vector.

3. Slow or Modern Epidemics.

Management of an epidemic involve step by step activities starting from forecasting to prevention for future occurrence.

STEPS OF EPIDEMIC MANAGEMENT

1. Forecasting of Epidemic.

2. Investigation of Epidemic.

3. Control of Epidemic.

4. Prevention of Epidemic.

FORECASTING OF EPIDEMICS

1.FORECASTING OF EPIDEMICS

Forecasting is an early warning system to get prepared to meet the challenges of impending epidemics.

It is more appropriate in cyclic and seasonal epidemics where the pattern has been studied from the past data.

By forecasting one may not totally prevent the epidemic , but definitely control its severity and spread to other areas.

Methods of forecasting

For forecasting the epidemic the prerequisite are –

Study of incidence and prevalence rate.

Disease specific morbidity and mortality rate.

Age and Sex wise morbidity and mortality rates.

The various data are tabulated month wise and year wise for the last three years (3 years) for comparison study of the pattern of disease.

Then the collected data is plotted on graph for immediate detection and visual appreciation through trend analysis of the disease.

Plotting of data on the map of local area helps in immediate assessment , whether the cases are grouped or clustered.

In spite of accurate forecasting an epidemic can not be aborted.

INVESTIGATION OF AN EPIDEMIC

The occurrence of an epidemic always signals some significant shift in the existing balance between the agent, host and environment.

In an unfortunate occurrence of an epidemic the case investigation must be started to confirm the epidemic.

Objectives of Investigation

1. To define the magnitude of the epidemic in terms of time, place and person.

2. To determine particular conditions and factors responsible for the occurrence.

3. To identify the cause, source and mode of transmission.

4. To make recommendations to prevent recurrence.

STEPS IN INVESTIGATION

1. Verification of diagnosis. 2. Confirmation of existence of epidemic. 3. Defining population at risk. 4. Rapid search for all cases in area. 5. Analysis of data. 6. Formulation of hypothesis. 7. Testing of hypothesis. 8. Evaluation of ecological factor. 9. Expand the search in other areas. 10.Writing the final report.

1. Verification of diagnosis.

The initial report may be spurious & arise from misinterpretation of the clinical features. It is therefore necessary to have the verification of diagnosis on the spot.

A clinical examination of sample cases are sufficient.

Laboratory investigations are most useful to confirm the diagnosis.

2. Confirmation of existence of epidemic.

An epidemic is said to exist when the number of cases (observed frequency) is in excess of the expected frequency for that population, based on past experience.

3. Defining population at risk.

Obtain a local area map containing natural landmarks, roads and location of all dwellings.

Counting the population by age and sex should be carried out.

4. Rapid search for all cases in area.

Medical survey should be carried out in defined area to identify all cases .

Epidemiological case sheet or Case Interview Form should be designed to collect relevant information.

The information should be collected relevant to the disease under study.

5. Analysis of data.

The data collected should be analyzed on ongoing basis under classical parameters -Time, Place and Person.

The characteristic of time, place and person should be rearranged in Agent-Host-Environment model.

TIME

Prepare a chronological distribution of dates of onset and construct an “EPIDEMIC CURVE”.

Epidemic Curve may suggest- 1. a time relationship with exposure to a

suspected source. 2. whether it is common source or

propagated epidemic. 3. whether it is a seasonal or cyclic

pattern.

PLACE

SPOT MAP (geographical distribution) of cases in relation of possible source of infection e.g. water supply, air pollution, food and occupation should be prepared.

Spot Map may provide evidence of - Source of disease. - Mode of spread.

PERSON

Analyze the data by age, sex, occupation and other possible risk factors.

We can determine the attack rates, case fatality rates for those who exposed.

6 & 7. Formulation and testing of hypothesis.

On the basis of time, place and person distribution and agent-host-environment model formulate the hypothesis to explain the epidemics in terms of –

(a) possible source. (b) causative agents. (c) possible modes of spread and (d) the environmental factors. Testing of all reasonable hypothesis

should be done with known facts.

8.Evaluation of Ecological factors

Ecological factors which have made epidemic possible should be investigated such as sanitary status of eating establishments, water supply, movement of human population and atmospheric changes.

One of the primary concern is to relate the disease to environmental factors to know the source, reservoir and modes of transmission.

9.Further investigation of population at risk.

A study of population at risk should be done to obtain additional information.

This may involve medical examination, screening test , examination of suspected food, faeces or blood samples.

10.Writing the final report.

The final responsibility of the investigative team is to prepare a written report to document the investigation’s findings and the recommendations.

The written report should be submitted in a standardized format to the public health authorities including the ministry of health.

Simultaneous to data collection & hypothesis formation, steps should be taken to control the epidemic.

These measures depend upon knowledge of etiologic agent, mode of transmission & other contributing factors.

Protective measures are necessary for patients (isolation & disinfection), their contacts (quarantine) and the community (immunization, etc).

CONTROL OF EPIDEMIC

To control of an epidemic one must have information -

1. Source / Causative organism.2. Dynamics of disease transmission.3. Mode of transmission.

Three principles of dynamics of disease transmission is used to control the epidemic-

1. Removal of source of infection. 2. Prevention of Transmission. 3. Vector control measures.

1. Removal of Source of infection

Treatment of infected cases.

Destruction of reservoir of infection.

Removal / correction of source of infection.

2. Prevention of transmission

Isolation of infected cases. Hand washing and personal protective

measures. Proper disposal of fomites. Improve environmental sanitation. Contact tracing .(family , neighbor). Screening of suspected cases. Quarantine of migrated cases. Health education. Increase resistance of suspects through

immunization and prophylactic drugs .

3. Vector Control measures

Prevention of breeding of mosquitoes, flies and fleas.

Destruction of adult vector through insecticide, pesticide.

Personal protection like use of mosquito net, use hot food and filtered water.

Increase personal hygiene. Improve environmental sanitation.

PREVENTION OF EPIDEMIC

There is saying that “more you sweat during the peace, less you bleed during the war.”

Appropriate measures at right time, right place in right quantity can prevent the severity of any epidemic.

Preventive measures

1. Improvement of the hygienic level of population.

2. Vaccination.3. Prophylactic disinfection.4. Registration and control of carriers.5. Health education.6. Environmental Measures.

6. Environmental Measures - Lighted and well ventilated houses.- Clean potable water supply.- Proper disposal of waste.- Adequate sewerage system.

EPIDEMIC PREPAREDNESS

Identify a nodal officer at state/district level. Strengthen routine surveillance system. Constitute rapid response teams. Train medical & other health personnel. Prepare a list of laboratories. List the “high risk” pockets. Establish rapid communication network. Undertake IEC activities. Ensure availability of essential supplies Inter-sectoral coordination.

The basic general lines of action during epidemics include – Preparedness and Interventions (investigations).

Success in dealing with an epidemic depends largely on the state of preparedness achieved in advance of any action.

THANK YOU