Week 5 - Foundations of Epidemiology.pdf

Biostatistics and Epidemiology

1. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
FOUNDATIONS OF
EPIDEMIOLOGY
LESTER JOSEPH M. BALLAD, RMT
KYLA JOY T. TORRADO, RMT
MELANIE JOY ARELLANO, RMT

2. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
LEARNING OUTCOMES
At the end of the lesson, the students must be able to:
•Explain the components of the Epidemiological Triad (agent, host,
environment) and their interrelationships in disease causation
•Differentiate modes of disease transmission (direct and indirect)
with examples of communicable diseases
•Describe the concepts of epidemic, endemic, and pandemic, and
analyze their implications for public health interventions
•Apply the principles of the Epidemiological Triad and disease
transmission to assess case studies of infectious disease
outbreaks
•Evaluate public health strategies to control epidemics, endemics,
or pandemics using epidemiological principles

3. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
EPIDEMIOLOGY
•Study of how disease is distributed in populations and the factors
that influence or determine this distribution
•Field of science dealing with the relationship of the various factors
which determine the frequencies and distribution of an infectious
process
•Study of the behavior of disease in the community rather than in
individual patients and includes the study of reservoirs and sources
of human disease
•The ultimate goal is to use this knowledge to
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4. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
HISTORICAL CHANGES IN CAUSE OF DEATH
•A major role of epidemiology is to provide a clue to changes that take
place over time in the health problems presenting in the community
•Developing countries still face infectious disease burdens but are
transitioning towards chronic diseases as they industrialize
•Epidemiologic transition: Shift from infectious to chronic diseases
due to:
oImprovements in sanitation, hygiene & antibiotics
oIncreased life expectancy
oLifestyle-related risk factors (smoking, obesity, pollution)

5. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y

6. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
EPIDEMIOLOGY & PREVENTION
•Identifying High-Risk Groups helps in targeting prevention programs
(e.g., early screenings for cancer in high-risk individuals)
•Three types of prevention:
1.Primary Prevention
2.Secondary Prevention
3.Tertiary Prevention
•Two approaches of prevention include Population-based approach
and High-risk approach

7. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y

8. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
HISTORICAL CASE STUDIES IN
EPIDEMIOLOGY
1.Ignáz Semmelweis and Childbed
Fever
•He specialized in obstetrics and
became interested in a major
clinical and public health problem
of the day – childbed fever
•In the early 19th century, childbed
fever was a major cause of death
among women shortly after
childbirth, with mortality rates
from childbed fever as high as 25%

9. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
2.Edward Jenner and smallpox
•In the late 18th century, 400,000
people died from smallpox each
year and a third of the survivors
became blind because of corneal
infections
•Jenner’s discovery (1796) –
smallpox’s cross immunization
with cowpox

10. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
3.John Snow and cholera
•Snow’s showed interest in the
epidemiology of cholera, a
disease that was a major problem
in England in the middle of the
19th century
•Cholera outbreaks were common
in the 1800s, causing severe
diarrhea and dehydration, often
leading to death
•At the time, most scientists
believed in the miasma theory

11. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y

12. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
THE DYNAMICS OF DISEASE PREVENTION
•In epidemiology of any disease or event, one studies the factor which
contribute to its causation and behavior – AGENT, HOST,
ENVIRONMENT

13. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
Factors of a Disease
1.The AGENT factors of disease
•Any element, substance or force whether living or non-living thing;
the presence or absence can initiate or perpetuate a disease
process
•This could be living or non-living things, physical or mechanical in
nature such as extremes of temperature, light electricity
•They could be chemical and biological
•Modes of transmission include: Direct and Indirect

14. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
2.The HOST factor of disease
•The organism (usually a human) that harbors the disease
•Can be influenced by:
oGenetic factors (susceptibility, immunity)
oNutritional status
oImmunity and previous exposure
oBehavior and lifestyle (hygiene, smoking, diet)

15. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
3.The ENVIRONMENT factor of disease
•Environment is the sum total of an organism’s external
surrounding conditions and influences that affect its life and
development
•Climate – certain diseases have seasonal distribution
•Geography & location – environment in certain areas contribute
to the occurrence of the disease
•Biologic environment – living environment of man consists of
plants, animals and fellow human beings

16. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y

17. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
EPIDEMIC, ENDEMIC, PANDEMIC
What’s the difference?
•The Centers for Disease Control and Prevention (CDC) describes an
epidemic as an unexpected increase in the number of disease cases
in a specific geographical area
•A disease outbreak is endemic when it is consistently present but
limited to a particular region. This makes the disease spread and
rates predictable
•The World Health Organization (WHO) declares a pandemic when a
disease’s growth is exponential. This means the growth rate
skyrockets, and each day cases grow more than the day prior

18. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
Term Geographic Spread Case Numbers Example
Epidemic Limited to a region or
country
Sudden rise above
expected levels
Ebola outbreak in
West Africa
Endemic Confined to a specific
area, occurring regularly
Stable levelsMalaria in sub-
Saharan Africa
Pandemic Global or multi-
continent spread
Widespread,
affects millions
COVID-19
pandemic

19. M T 1 0 5 3 : B I O S T A T I S T I C S & E P I D E M I O L O G Y
ISOLATION & QUARANTINE
•Isolation, as applied to patient, separation for the period of
communicability, of infected persons or animals from others in such
places and under such conditions as to prevent or limit the effect of
the direct or indirect transmission of the infectious agent from those
infected to those who are susceptible or who may spread the disease
agent
•Quarantine is the restriction of the activities of a well persons or
animals who have been exposed to a case of communicable diseases
during its period of communicability to prevent disease transmission
during incubation of infection should occur