Epidemiologic transition

Epidemiological Transition
By: Dr Animesh Gupta
6/6/2017 1

Epidemiological Transition
1. Introduction
2. Theories
3. Mechanisms
4. Indicators
5. Conclusion
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Introduction
• The general shift from acute infectious and
deficiency diseases characteristic of
underdevelopment to chronic non-
communicable diseases characteristic of
modernization and advanced levels of
development is usually referred to as the
"epidemiological transition".
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• The epidemiologic transition describes
changing patterns of population distributions
in relation to changing patterns of mortality,
fertility, life expectancy, and leading causes of
death.
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• The very term “epidemiologic transition” raises
the question of transition from what to what?
• There are two major components of the
transition:
(1) Changes in population growth trajectories and
composition, especially in the age distribution
from younger to older, and
(2) Changes in patterns of mortality, including
increasing life expectancy and reordering of the
relative importance of different causes of death.
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Omran’s Theory
• Proposition One. The theory of epidemiologic
transition begins with the major premise that
mortality is a fundamental factor in population
dynamics.
• Proposition Two. During the transition, a long-
term shift occurs in mortality and disease
patterns whereby pandemics of infection are
gradually displaced by degenerative and man-
made diseases as the chief form of morbidity and
primary cause of death.
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• The first transition phase, called the “Age of
Pestilence and Famine”, is characterized by
high and fluctuating mortality rates, variable
life expectancy with low average life span, and
periods of population growth that are not
sustained.
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• The second transition phase is characterized as
the “Age of Receding Pandemics”, and is
marked by declining mortality rates an increase
in average life expectancy from about 30 years
to about 50 years of age, and more sustained
population growth that eventually becomes
exponential.
• Early modern period - characterized by a shift in
patterns of disease and mortality from primarily
infectious diseases to what have come to be
called “chronic” diseases.
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• The third transition phase is termed the “Age
of Degenerative and Man-Made Diseases”
• Infectious disease pandemics are replaced as
major causes of death by degenerative
diseases, and infectious agents as the major
contributor to morbidity and mortality are
overtaken by anthropogenic causes
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• Proposition Three. During the epidemiologic
transition the most profound changes in
health and disease patterns obtain among
children and young women.
• Proposition Four. The shifts in health and
disease patterns that characterize the
epidemiologic transition are closely associated
with the demographic and socioeconomic
transitions that constitute the modernization
complex.
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• Proposition Five. peculiar variations in the
pattern, the pace, the determinants and the
consequences of population change.
• These three models are
 The classical or western model (European
countries),
 The accelerated model (Japan)
 The contemporary or delayed model
(Developing Country)
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Epidemiological transition:
An Indian perspective
• Overweight and obesity in childhood is
increasing at an alarming rate in the
developed countries, and the same is
expected to happen in developing economies
as their prosperity rises.
• Road Traffic accidents, STI
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Mechanisms involved in
Epidemiological Transitition
Demographic changes
• As populations become healthier, a reduction
in mortality, particularly of infants and
children, usually occurs, followed later by a
fall in fertility rates.
• Diseases that more frequently affect elderly
people, such as cancer and cardiovascular
diseases.
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Changes in risk factors
1. Biological factors
• It is well known that microorganisms constantly
undergo changes that enable them to cope with
an increasingly hostile environment.
• This adaptive process involves finding and
exploiting weaknesses in the defences of the host
and can happen by means of several
mechanisms: alteration in antigenic identity,
emergence of drug-resistant strains and dual
infection
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2. Environmental factors
• There is conclusive evidence that certain
changes in the patterns of diseases, in
particular a decrease in the occurrence of
communicable diseases such as cholera, are
the result of the development of
environmental sanitation, particularly a clean
water supply, sanitary disposal of waste and
proper housing.
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• On the other hand, environmental factors may
increase the incidence of infectious diseases if
they offer opportunities for transmission of
etiological agents from the reservoirs of
infection to susceptible hosts, for example by
promoting breeding of vectors of diseases or
because of overcrowding
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a) Exposure to environmental pollutants
• One of the main growing environmental
pollutants is ionizing radiation from medical and
occupational contacts and from commercial and
military use of atomic energy.
• Excessive use of insecticides both in agriculture
and in public health for vector control is another
source of significant environmental pollution.
• Excessive use of cars - source of air pollution and
its effect on developing lung cancer is well
documented
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b) Overcrowding
• Migration from villages to towns due to
industrialization and the development of high
density urban areas facilitate the spread of
infections, especially of diseases spread by
droplets and those related to atmospheric
pollution
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3. Social, cultural and behavioural factors
• The shift from an agricultural to an industrial
society and its accompanying process of
modernization produce changes that affect
people's health.
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a) Changes in community relationships
• Modernization has adversely affected close
community ties, which used to provide
opportunities to share sorrow and happiness and
to alleviate stress.
• An evident example of maladjustment due to
urbanization is the traumatic encounter of rural
youth with urban values. This frequently has a
serious impact on mental health.
• Another example of the change in community
relations is the care of the elderly.
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b) Changes in lifestyle
• Conditions of life and the way people live and
work (lifestyles) have been a cause of many
diseases, particularly non-communicable
diseases.
• Mass media (television, radio, newspapers,
journals, magazines, books, etc.), which are
one of the main manifestations of
modernization
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c) Decreased concern about moral values
• Urbanization and industrialization - by a
decreasing concern for moral and religious values
and the appearance of lifestyles that have led to
changes in the pattern of some diseases.
• Sexual revolution- sexual activity - the rapid
spread of STDs.
• An increase in the consumption of alcohol and of
smoking are also evidence of decreased concern
for religious values.
Their effects on health are well known, as they are
major risk factors for noncommunicable diseases.
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4.Practices of modern medicine
• Development of antibiotics and antimicrobial
agents, insecticides, vaccines and diagnostic
and therapeutic technologies, have resulted in
remarkable progress in the prevention and
control of many diseases and in the effective
management of many others.
• The cure-oriented intervention techniques of
modern medicine increasing number of
manipulative procedures have been
responsible for some side effects of diseases.
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• The spread of viral hepatitis B and C and HIV
infection through the use of contaminated
needles and through unscreened blood
transfusions is another example in which
intervention becomes a source of infectious
disease.
6/6/2017 29

Indicators of the epidemiological
transition
• Mortality indicators
• Morbidity indicators
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Conclusions and Recommendation
• The changing pattern of diseases observed
over recent years, from acute infectious and
deficiency diseases to the chronic non-
communicable diseases, is a continuous
process of transformation with some diseases
disappearing and others appearing or
reappearing
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• It is clear that infectious diseases are still an
important public health problem and a major
cause of death and of illness and will continue
to be so for future generations.
• At the same time, noncommunicable diseases
are coming to the forefront as causes of illness
and death, especially in countries where it
used to be possible to control many
communicable diseases.
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• The public has a major role to play, and hence
the necessity for public health education and
promotion of healthy lifestyles.
• Health education efforts to achieve positive
behavioural changes are essential for the
prevention and control of diseases.
• A carefully conceived media campaign can
have a beneficial effect on changing
behaviours related to the occurrence of
diseases, such as smoking, obesity, alcohol
consumption and other dangerous behaviour
and lifestyles.
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ONION PEEL PHENOMENON
• OLD DISEASES FADE AWAY
GIVING PLACE TO THE NEW
ONES
• JUST LIKE THE LAYERS OF THE
ONION, THE OLD DISEASES
WANE AND GIVE PLACE TO
NEWONES.
• INFECTIOUS ONES WILL BE
REPLACED BY NON–
INFECTIOUS ONES TO BE
REPLACED LATER
BY PERSONAL AND
BEHAVIORAL PROBLEMS.
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• An emerging disease is one that has appeared in
a population for the first time, or that may have
existed previously but is rapidly increasing in
incidence or geographic range.
• Re-emerging diseases are due to the
reappearance of, and an increase in, the number
of infections from a disease which is known, but
which had formerly caused so few infections that
it had no longer been considered a public health
problem.
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References
• Michael H Merson, International Public Health: Diseases,
Programs, systems and Policies, 2nd ed, 273-277
• Robert E Mckeown, The Epidemiological Transition:
changing patterns of mortality and population dynamics
[Am J Lifestyle Med. 2009 July 1; 3(1 Suppl): 19S–26S.
doi:10.1177/1559827609335350.]
• Omran AR. The Epidemiologic Transition. Milbank Mem
Fund Q 1971;49:509–538. [PubMed:5155251, last accessed
on 24/10/13]
• M.H. Wahdan, The epidemiological transition
[http://www.cba.edu.kw/eqbal/epidemiological_transition.
htm]
• Park’s textbook of preventive and social medicine, K. Park,
22nd edition, 328-29.
6/6/2017 36

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