Introduction to epidemiology.

1. Unit VIII
EPIDEMIOLOGY
Presented By:
Sapana Dahal
M.Sc.Nursing 1st year
CoN,BPKIHS
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2. CONTENTS
1.Introduction
2.History
3.Definitions
4.Components
5.Aims
6.Epidemiological Approach
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3. CONTENTS (Conti..)
8. Measurements in Epidemiology
9. Tools of measurement
10. Uses of Epidemiology
11. Various terms used in Epidemiology
12. References
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4. OBJECTIVES
At the end of the session, participants will be
able to explain about epidemiology.
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6. Introduction
The word epidemiology comes from the
Greek word, Epi which means on or upon,
demos which means people,population or
community and logos means study.
It does not only cover the study of disease
distribution and prevention but also health and
health related events occurring in the human
population
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7. Introduction (Conti..)
It is data-driven and relies on a systematic and
unbiased approach to the collection, analysis, and
interpretation of data.
It is a quantitative discipline that relies on a
working knowledge of probability, statistics, and
sound research methods.
It is not just a research activity but an integral
component of public health, providing the
foundation for directing practical and appropriate
public health action based on this science and
causal reasoning.
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11. History of Epidemiology (cont..)
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12. DEFINITIONS
It is the branch of medical science which treats
epidemics.(Parkin, 1873)
The science of the mass phenomena of
infectious diseases.(Frost,1927)
The study of disease,any disease as a mass
phenomenon.(Greenwood,1934)
The study of distribution and determinants of
disease frequency in man.(MacMahon,1960)
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13. Definitions (Conti..)
The study of distribution and determinants of
health related states or events in specified
populations and the application of this study to
the control of health problems. (John M
Last,1988)
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14. Components
1. Disease Frequency
2. Distribution of Disease
3. Determinants of Disease
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15. Aims of Epidemiology
•To eliminate or reduce the health problems or
its consequences.
•To promote the health and well- being of society
as a whole.
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16. Epidemiological Approach
1.Asking Questions(On Problems)
What are the actual and potential health
problems its manifestations and characteristics?
•What is the problem?
•Where is the problem occurring in terms of
place?
•Who are affected by the problem in reference to
age, sex, social class..?
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17. Asking Questions(On Problems)
• When does it happen in terms of day, month,
season,….?
• What is the problem occurring in terms of
causative factors?
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18. Epidemiological Approach(Conti.)
Asking Questions (On Health Action)
•What can be done to solve the problem?
•What can be the consequences of the action?
•What and how resources can be used to solve
the problem? What action can be taken by the
community to prevent and manage problem?
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19. Asking Questions (On Health
Action)
•What actions taken by health and other sectors?
•What difficulties can be faced during problem
solving and how to overcome them?
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20. Epidemiological Approach(Conti..)
2.Making Comparisons
Comparison can be made based on groups either
two or more groups- one group having the
disease or exposed to risk factor and the other
not having the disease or not exposed to the risk
factor or the comparison can be made among the
individuals.
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21. Epidemiological Approach(Conti..)
Important factor to be considered while making
comparisons is to know both the groups are
similar so that the like can be compared with the
like.
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22. Scenario
ACT Alert Nepal - Diarrhoea
outbreak No. 17/2009
Brief description of emergency: A diarrhoea
outbreak has badly affected some hill districts in
the mid - and far -western regions of Nepal. The
first case of diarrhoea was reported in Rokaya
Gaon of Jajarkot district on 3 May 2009. The
epidemic has now spread to nine hill districts.
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23. Scenario(Conti..)
According to a report presented by UNICEF in
the WASH cluster on 23 July 2009, around
100,000 families in 100 Village Development
Committees (VDCs) are affected.
The deaths are mainly attributed to lack of clean
drinking water, poor sanitation and hygiene,
along with a lack of medicine and good nutrition.
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24. Scenario(Conti..)
Because of winter drought, water sources have
dried up and recent rainfall has increased the risk
of using contaminated water. Availability of
water is low in the affected areas and open air
defecation is common practice.
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25. Scenario(Conti..)
National and international response:
The Epidemiology and Disease Control Division
(EDCD) of the Government of Nepal, the Nepal
Army, WHO, UNICEF and some international
and national NGOs are providing relief supplies
and education materials to the affected districts.
Some medical teams have also be deployed to
the affected districts
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26. Outbreak Investigation of Diarrheal
Diseases in Jajarkot
Background: Diarrhea is a major public health
problem in Nepal. Recently, there was an
outbreak of diarrheal diseases in different
districts of mid and far western region of Nepal
and the most affected district was Jajarkot.
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27. Outbreak Investigation of Diarrheal
Diseases in Jajarkot(Conti..)
The objective of this study was to detect the
causative organism and analyze the epidemic
outbreak patterns of diarrhea in selected health
institutions in Jajarkot district, in terms of their
demographic characteristics and laboratory
findings of stool specimens.
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28. Outbreak Investigation of Diarrheal
Diseases in Jajarkot(Conti..)
Stool samples were collected purposively to
identify the agents of diarrheal diseases.
Results: Out of the total 13 stool samples tested,
5 were diagnosed as harboring Vibrio cholerae.
The AR and CFR were calculated to be 8.2% and
1% respectively.Age groups 15-44 years;male
and female were approximately equally affected.
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29. Epidemiological Approach for the
Scenario
What is the problem or event?
-Diarrhoeal Outbreak
Where is the problem occurring?
- Mid - and far -western regions of Nepal specially
Jajarkot district. Jajarkot District a part of Karnali
Province. The district, with Khalanga as its district
headquarters, covers an area of 2,230 km2 (860 sq
mi)[1] and has a population of 171,304 in 2011
Nepal census.
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30. Epidemiological Approach for the
Scenario(Conti..)
Who are mostly affected by the outbreak?
-Men and women were equally affected of the
age group 15-44.
When does it happen?
-In the month of May/ June which is the pre-
monsoon and monsoon season.
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31. Epidemiological Approach for the
Scenario(Conti..)
Why is the problem occurring?
- Lack of clean drinking water, poor sanitation
and hygiene, along with a lack of medicine and
good nutrition.
- Rainfall has increased the risk of using
contaminated water. Availability of water is low
in the affected areas and open air defecation is
common practice.
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32. Epidemiological Approach for the
Scenario(Conti..)
What was done to solve the problem?
-Stool sample were sent to the laboratory
- RRT were mobilized
What was the consequences of the action?
-Causative agent was identified (Vibrio Cholera)
-Information reached to the central level
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33. Epidemiological Approach for the
Scenario(Conti..)
What action was taken by the community to
prevent and manage problem?
-Health and hygiene promotion
-Water testing
-Miking in high-risk areas
-Active case finding and early detection by
FCHVs, including referral to health facilities
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34. Epidemiological Approach for the
Scenario(Conti..)
What actions taken by health and other
sectors?
-Reporting of the disease occurrence by the
local, district and regional hospitals to the
central level EDCD.
-Mobilization of RRT in the outbreak area
-Various NGOs and INGOs provide relief
supplies to the affected area.
-Mass Cholera vaccination campaign launched
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35. Epidemiological Approach for the
Scenario(Conti..)
What difficulties were faced during problem
solving and how to overcome them?
-No dedicated budget
-Limited medical supplies
-Lack of skilled manpower
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36. Outbreak of cholera in Tilathi VDC
Saptari Nepal
Background: On 2011, Cluster of cholera cases was
reported in the Tilathi VDC of Saptari, Nepal.
Methods: Demographic and clinical details were
collected from the suspected case-patients, and the
outbreak was described by time, place, and person.
Focus group discussion and Key informant
interview were conducted to assess the practice of
sanitation, source of drinking water and probable
cause of diarrheal disease.
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37. Outbreak of cholera in Tilathi VDC
Saptari Nepal(Conti..)
Five stool samples and 10 water samples of tube
well and ponds were collected and
microbiological study was done in BPKIHS
Dharan.
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38. Outbreak of cholera in Tilathi VDC
Saptari Nepal(Conti..)
Results:
A total of 111 persons suffered with diarrhea and
2 died of it (attack rate 3.05%, case fatality rate
1.8%). All age groups were affected with disease
(median age 26 yrs) and males were affected
more than females. Descriptive epidemiology
suggested the clustering of cases were around the
pond where they clean utensils, take bath and
wash clothes.
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39. Outbreak of cholera in Tilathi VDC
Saptari Nepal(Conti..)
The Vibrio cholerae 01 El Tor, Ogawa serotype
was isolated in 03 out of 05 suspected stool
samples and in all three of the pond water
samples. They reported that most of the houses
do not have the toilet and people do not wash
their hands regularly with soap and water after
defecation.
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40. Outbreak of cholera in Tilathi VDC
Saptari Nepal(Conti..)
Conclusion:
Vibrio cholerae was the causative agent behind
the outbreak and probable source of infection
was the problematic pond water which they used
for different purpose. Immediate chlorination of
the pond was recommended to halt further
spread of the epidemics.
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41. Epidemiological Approach (Conti..)
Making Comparisons
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Jajarkot Outbreak Saptari Outbreak
Age -Group 15-44 years(mostly
affected)
All Age groups
Gender Male=female Male˃ female
Causative Agent Vibrio Cholera Vibrio Cholera
Risk factors Lack of proper sanitation Lack of proper sanitation
Interventions Chlorination,Health
Education
Chlorination,Health
Education

42. Measurements in Epidemiology
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Epidemiology focuses on the measurement of
mortality and morbidity in human populations
therefore the fore most requirement is the
definition of what is to be measured and
establishment of the criteria or standards by
which it can be measured.

43. Measurements in Epidemiology(Conti.)
•Measurement of mortality
•Measurement of morbidity
•Measurement of disability
•Measurement of natality
•Measurement of disease attributes
•Measurement of health services
•Measurement of risk factors
•Measurement of demographic variables
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44. Tools of Measurement
Case Count
It refers to the number of cases of the disease or
other health phenomenon being studied.
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45. Tools of Measurement(Conti..)
Rates
It measures the occurrence of some particular
event in a population during a given time period
Ratio
It expresses a relation in size between two
random quantities
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46. Tools of Measurement (Conti..)
Proportions
It is a ratio which indicates the relation in
magnitude of a part of a whole.
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47. Uses of Epidemiology
• To study historically the rise and fall of diseases in
the population
• For community diagnosis
• Planning and evaluation
• Evaluation of individual risk and chances
• Syndrome identification
• Completing the natural history of disease
• Searching for the causes and the risk factors
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48. Terms used in Epidemiology
Outbreak : It refers to the occurrence of new
case(s) of disease in a previously unexposed
population. Eg.Monkey pox
Cluster :an unusual aggregation, real or
perceived, of health events that are grouped
together in time and space and that is reported to
a public health department.(CDC 1990)
Eg.Colds,flu.
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49. Terms used in Epidemiology (Conti.)
Epidemic:
Endemic:
Sporadic:It refers to a disease agent or health
condition that occurs infrequently or irregularly
in a population.Eg.tetanus
Hyperendemic :It refers to persistent high levels
of occurrence of a disease agent or health
condition in a population
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50. Terms Used in Epidemiology (Conti.)
Epidemic proportion :It has been used to
describe large numbers of cases of chronic
disease in a population. Example: The high
prevalence of diabetes and obesity in the U.S.
Causation : Disease results from the interaction
between the agent and the susceptible host in the
environment that supports transmission of the
[disease] agent from a source to that host
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51. QUERRY?????
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52. REFERENCES
1.Park K.Textbook of Preventive and Social
Medicine,Jabalpur:BhannarsidasPublishers,2019(25t
h edition)
2.Davies JB. Preventive medicine, community health
and social services. Preventive medicine, community
health and social services.1971(2nd Edition).
3.Bonita, Ruth, Beaglehole, Robert, Kjellström, Tord
& World Health Organization. (2006). Basic
epidemiology, 2nd ed. World Health Organization.
https://apps.who.int/iris/handle/10665/43541
4.https://www.cdc.gov/publichealth101/epidemiolog
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