Epidemic is defined as – “ the unusual
occurrence of the disease or health
related event in a community or region,
clearly in excess of “expected
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.
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
1. Forecasting of Epidemic.
2. Investigation of Epidemic.
3. Control of Epidemic.
4. Prevention of Epidemic.
Forecasting is an early warning system to get
prepared to meet the challenges of impending
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.
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
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.
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.
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
4. To make recommendations to prevent
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.
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
Laboratory investigations are most useful to
confirm the diagnosis.
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
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.
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
The information should be collected relevant to
the disease under study.
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-
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
2. whether it is common source or propagated
3. whether it is a seasonal or cyclic pattern.
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.
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.
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.
Ecological factors which have made epidemic
possible should be investigated such as
sanitary status of eating establishments, water
supply, movement of human population and
One of the primary concern is to relate the
disease to environmental factors to know the
source, reservoir and modes of transmission.
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.
The final responsibility of the investigative
team is to prepare a written report to document
the investigation’s findings and the
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
These measures depend upon knowledge of
etiologic agent, mode of transmission & other
Protective measures are necessary for patients
(isolation & disinfection), their contacts
(quarantine) and the community
To control of an epidemic one must have
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.
Treatment of infected cases.
Destruction of reservoir of infection.
Removal / correction of source of infection.
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.
Increase resistance of suspects through
immunization and prophylactic drugs .
Prevention of breeding of mosquitoes, flies and
Destruction of adult vector through insecticide,
Personal protection like use of mosquito net,
use hot food and filtered water.
Increase personal hygiene.
Improve environmental sanitation.
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.
1. Improvement of the hygienic level of
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.
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
The basic general lines of action during
epidemics include – Preparedness and
Success in dealing with an epidemic depends
largely on the state of preparedness achieved in
advance of any action.