iceberg phenomenon.pptx

Presentedby
Deepa Manandhar
Lecturer
CommunityHealthNursing

Pre test
Floating tip of the ice berg represents
a. Carriers
b. Undiagnosed cases
c. Clinical cases
d. Latent cases
ANS: C

Iceberg phenomenon
 Community may be compared to an iceberg.
 The floating tip of the iceberg represents what the
physician sees in the community i.e. clinical cases
 Submerged is the part explored and made visible by
the epidemiologists.

Iceberg phenomenon
• Vast submerged portion of the iceberg represents the
hidden mass of disease i.e. latent, inapparent, pre-
symptomatic and undiagnosed cases and carriers in
the community.
• The "water – line" represents the boundary line
between the apparent and inapparent disease.

Iceberg phenomenon
• In some diseases e.g. hypertension, diabetes, anemia)
the unknown morbidity (i.e. the submerged portion of
the iceberg) far exceeds the known morbidity.
• The hidden part of the iceberg constitutes an
important, undiagnosed reservoir of infection or
disease in the community, and its detection and
control is a challenge to modern techniques in
preventive medicine.

Iceberg phenomenon
• Example

Dynamics of disease
transmission
Presented by
Deepa Manandhar
Lecturer
Community Health Nursing

Pre test
The person, animal, object or substance from which an
infectious agent passes or is disseminated to the host is
a) Reservoir
b) Source of Infection
c) Host
d) Cases
ANS: Source of infection

Dynamics of disease Transmission
(Chain of Infection)
• Communicable diseases are transmitted from the
reservoir/ source of infection to susceptible host.
• There are three links in the chain of transmission.

Dynamics of disease Transmission
(Chain of Infection)
Source and Reservoir Modes of transmission Susceptible host

Source of Infection
• The source of infection is defined as “the person,
animal, object or substance from which an infectious
agent passes or is disseminated to the host”.

Reservoir
“Any person, animal, arthropod, plant, soil, or
substance (or combination of these) in which an
infectious agent lives and multiplies, on which it
depends primarily for survival, and where it
reproduces itself in such manner that it can be
transmitted to a susceptible host”.

Types of Reservoiur
Human
Animal
Non living things

Human reservoir
• The most important source or reservoir of infection
for human is man himself.
• Human may be
 Cases
 Carriers

Human reservoir
Human reservoir
cases carriers
According to spectrum of disease:
•Clinical cases
(mild/severe-typical/atypical)
•Sub-clinical cases
•Latent infection cases
•Primary case
•Secondary cases
Type:
•Incubatory
•Convalescent
•healthy
Duration:
•Temporary
•Chronic
Portal of exit:
•Urinary
•Intestinal
•Respiratory
•blood

Cases
• A case is defined as “ a person in the population
having the particular disease, health disorder or
condition under investigation”.
• The presence of infection in host may be :
 Clinical
 Sub clinical
 Latent

Clinical cases
• Clinical illness may be mild or moderate, typical or
atypical, severe or fatal.
• Mild cases may be more important source of infection
than severe cases

Subclinical cases
• Also known as inapparent, missed cases.
• The disease agent may multiply in the host but does
not manifest itself by signs and symptoms.
• May be detected only by laboratory test

Latent infection
• Infectious agent lies dormant within the host
without symptoms (and often without
demonstrable presence in blood, tissue or
bodily secretions of the host.

In epidemiological terminology
• Primary case: first case of a communicable disease
introduced into the population.
• Secondary case: develops from contact with primary
cases.
• Index case: first case which comes to the attention of
investigator.

Carrier
• In some diseases, either due to inadequate treatment
or immune response, the disease agent is not
completely eliminated, leading to a carrier state.

Carrier
• As a rule a carriers are less infectious than
cases, but epidemiologically, they are more
dangerous than cases.

Carrier
• Defined as an infected person or animal that harbours
a specific infectious agents in the absence of
discernible clinical disease and serves as a potential
source of infection for other.

Carrier
The elements in a carrier state are:
• The presence of disease agent in the body.
• The absence of recognizable signs and
symptoms
• Spread of disease agent in the discharges or
excretions

Classification of Carrier
A. TYPE
 Incubatory
 Convalescent
 Healthy
B. DURATION
 Temporary
 Chronic

Classification of Carrier
C. PORTAL OF EXIT
 Urinary
 Intestinal
 Respiratory
 Others

Incubatory Carrier
 Carriers which spread the infectious agent during the
incubation period of disease.
 This usually occurs during the last few days of
incubation period.

Convalescent Carrier
Carriers which continue to spread disease during the
period of convalescence.

Healthy Carrier
• They are victims of sub clinical infection who have
developed carrier state without suffering from overt
disease.

Carrier acc to duration
(a) Temporary carriers:- Carriers which spread
infectious agent for short period of time
(b) Chronic carriers:- Carriers which spread
infectious agent for indefinite period

Portal of Exit
Urinary
 Intestinal
Respiratory
 Others –(skin eruptions, open wounds, blood)

Animal Reservoir
• The source of infection may sometimes be animals
and birds.
• The diseases and infections which are transmissible to
man from vertebrate are called zoonoses.
Eg :- Rabies, Yellow Fever, Influenza

Reservoir in non-living things
• Soil and inanimate matter can also act as reservoir of
infection

Introduction
Communicable diseases are transmitted from reservoir
to host in many different ways

Modes of Disease Transmission
• Direct contact
• Droplet infection
• Contact with soil
• Inoculation into skin or mucosa
• Transplacental (vertical)
A.Direct
• Vechicle borne
• Vector borne
• Air borne
• Fomite borne
• Unclean hands and fingers
B. Indirect

Direct transmission
Direct Contact:
implies direct and essentially immediate transfer of
infectious agents from the reservoir or source to a
susceptible individual, without an intermediate
agency.

Direct transmission
Direct contact

Direct transmission
Direct Contact:
• Direct contact not only reduces the period for which
the organism will have to survive outside the human
host but also ensures a larger dose of infection.
• Diseases transmitted by direct contact include STD
and AIDS, leprosy, leptospirosis, skin and eye
infections.

Direct transmission
Droplet infection
• This is direct projection of spray of droplets of saliva
and nasopharyngeal secretions during coughing,
sneezing, talking or spitting.

Direct transmission
Droplet infection
• Particle size: 10mmm or > filtered by nose
5mmm or < can reach the alveoli
• The droplet spread is usually limited to a distance of
30-60 cm between source and host
• Eg: Respiratory Infections, Common Cold,
Tuberculosis, Diphtheria

Direct transmission
Contact with soil
• The disease agent may be acquired by direct exposure to the
disease agent in the soil
• Eg :- hook worm, tetanus.

Direct transmission
Inoculation into skin or mucosa:
• Disease agent may be inoculated directly into the
skin or mucosa

Direct transmission
Transplacental (or vertical) transmission:

Indirect transmission
• 5 –F`s
 Flies
 Fingers
 Fomites
 Food
 Fluids

 essential requirement for indirect transmission is that
the infectious agent must be capable of surviving
outside the human host in the external environment
and retain its basic properties of pathogenesis and
virulence till it finds a new host.

1.Vechicle borne
2.Vector borne
3.Air borne
4. Fomite - borne
5. Unclean hands and
fingers
a. Mechanical b . Biological
a. Droplet nuclei b. Dust

1. Vechicle borne
Transmission of the infectious agent through the
agency of water, food, raw vegetables, fruits, milk,
blood etc.

2. Vector – borne
Vector is defined as an arthropod or any living carrier
that transports an infectious agent to a susceptible
individual.

Classification of vector borne disease:-
1. By vector
– Invertebrate Eg-arthropods( flies, mosquitoes,
cockroach, ticks, mites, bugs)
– Vertebrate Eg-mice, rodents

2. By transmission chain
• Man and a non vertebrate host (man-mosquitoe- man
in malaria)
• Man , another vertebrate host and a non vertebrate host
(bird-arthropod-man)
• Man and 2 intermediate host (man-cyclops-fish-man)

By methods in which vectors transmit agent
 Biting
 Scratching
 Regurgitation

• By methods in which vectors are involved in the
transmission of parasite
 Mechanical transmission
 Biological transmission

3. Air Borne
 Droplet nuclei
• Tiny particles (1-10 microns range) that represents
the dried residue of droplets
 Dust

4. Fomite Borne

Susceptible Host
Successful Parasitism
Portal
of entry
Site of
election
Portal
of exit
Survival in
the
environment

Portal of entry
• Infectious agent enter the host
Eg:
 Respiratory tract
 Genito urinary tract
 Skin

Site of Election
• In the body the disease agent finds appropriate tissue
for multiplication and survival.

Portal of Exit
The disease agent finds a way out of the body

Survival In The Environment
After leaving the human body the organism must
survive in the external environment for sufficient
period till a new host is found

Disease control
Is reducing the transmission of disease agent to
such a low level that it ceases to be a public
health problem.

Disease control
The term “disease control” describes operation
aimed at reducing:
The incidence of disease
The duration of disease, and consequently the risk
of transmission
The effects of infection, including both the
physical and psychosocial complications
The financial burden to the community.

Disease elimination
 It is complete interruption of transmission of
disease in a defined geographical area.
 Disease elimination is a geographical term, i.e.
can be used only for a country or a region.
 Disease elimination supports in disease
eradication.

Disease eradication
 Is complete extermination of organism
 Is tearing out by roots of a disease
 Exhibits “all” or “none phenomenon

Disease eradication
 Permanent reduction to zero of the worldwide
incidence of infection caused by a specific
agent as a result of deliberate efforts;
intervention measures are no longer needed.
Example: smallpox.

Terminologies
• Control: The reduction of disease incidence, prevalence,
morbidity or mortality to a locally acceptable level as a result
of deliberate efforts; continued intervention measures are
required to maintain the reduction. Example: diarrhoeal
diseases.
• Elimination of disease: Reduction to zero of the incidence of a
specified disease in a defined geographical area as a result of
deliberate efforts; continued intervention measures are
required. Example: neonatal tetanus.

Terminologies
• Eradication: Permanent reduction to zero of the worldwide
incidence of infection caused by a specific agent as a result of
deliberate efforts; intervention measures are no longer needed.
Example: smallpox.

Disease control…
Disease control involves all the measures
designed to prevent or reduce as much as
possible the incidence, prevalence and
consequences of disease.

Disease control…
Disease control measures include
1. Controlling the reservoir
2. Interruption of transmission
3. Protection of the susceptible host.

1. Controlling the Reservoir
General measures of reservoir control comprise:
 Early diagnosis
 Notification
 Isolation
 Treatment
 Quarantine
 Surveillance

1. Earlydiagnosis:
The first step in the control of a communicable
disease is its rapid identification.
It is the cornerstone on which the disease
control is built.

Early diagnosis is needed for:
Treatment of patient
Epidemiological investigation
To trace the source of infection from the known or
index case to the unknown.
To study the time, place and person distribution.
For the institution of prevention and control
measures

2. Notification:
Once an infectious disease has been
detected or suspected is should be notified
to local health authority, whose
responsibility is to put into operation
control measures, including the provision of
medical care to patients.

2. Notification:
 Important source of epidemiological
information.
 Enables early detection of disease
outbreaks, which permits immediate
action to be taken by the health authority
to control their spread.

1.Controlling the Reservoir
3. Epidemiological Investigation:
 An epidemiological investigation is called for
whenever there is a disease outbreak.
 Investigation covers the identification of the source of
infection and of the factors influencing its spread in
the community.

1.Controlling the Reservoir…
3. Epidemiological Investigation:
 Include geographical situation, climatic condition,
social, cultural and behavioral patterns, and more
importantly the character of the agent, reservoir, the
vectors and vehicles, and the susceptible host
populations.

1.Controlling the Reservoir…
4. Isolation:
 Oldest communicable disease control measure.
 It is defined as "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 direct or
indirect transmission of the infectious agent from those
infected to those who are susceptible, or who may spread the
agent to others".

1. Controlling the Reservoir…
4. Isolation:
 The purpose of isolation is to protect the
community by preventing transfer of infection
from the reservoir to the possible susceptible
hosts.

4. Isolation:
 Duration of isolation is determined by the duration of
the communicability of the disease and the effect of
chemotherapy on infectivity.

5. Treatment:
 Many communicable diseases have been tamed by
effective drugs.
 The objective of treatment is to kill the infectious agent
when it is still in the reservoir, i.e., before it is
disseminated.
 Treatment reduces the communicability of disease, cuts
short the duration of illness and prevents development
of secondary cases.

5. Treatment:
 In some diseases (e.g., syphilis, tuberculosis, and
leprosy), early diagnosis and treatment is of primary
importance in interrupting transmission. Treatment is
also extended to carriers.
 Treatment can take the form of individual treatment
or mass treatment

6. Quarantine:
Defined as "the limitation of freedom of movement of
such well persons or domestic animals exposed to
communicable disease for a period of time not longer than
the longest usual incubation period of the disease, in such
manner as to prevent effective contact with those not so
exposed".

6. Quarantine:
 Quarantine measures are also "applied by a health
authority to a ship, an aircraft, a train, road
vehicle, other means of transport or container, to
prevent the spread of disease, reservoirs of
disease or vectors of disease".
 In contrast to isolation, quarantine applies to
restrictions on the healthy contacts of an
infectious disease.

7. Surveillance:
 The continuous scrutiny of the factors that
determine the occurance and distribution of
disease and other conditions of ill-health.
 Is the ongoing systematic collection and
analysis of data and the provision of
information which leads to action being taken
to prevent and control a disease.

2.Interruption of Transmission
 A major aspect of communicable disease control relates
to "breaking the chain of transmission" or interruption
of transmission.
 This may mean changing some components of man's
environment to prevent the infective agent from a
patient or carrier from entering the body of susceptible
person.

2.Interruption of Transmission
 For example, water can be a medium for the
transmission of many diseases such as typhoid,
dysentery, hepatitis A, cholera and gastroenteritis.
Water treatment will eliminate these diseases.
 Depending upon the level of pollution, this may vary
from simple chlorination to complex treatment.

Transmission of faecal borne disease

3. The susceptible host…
The third link in the chain of transmission is the
susceptible host or people at risk. They may be
protected by one or more of the following strategies.
a)Active immunization
b)Passive immunization
c)Combined passive and active immunization
d)Chemoprophylaxis
e) Nonspecific measures

a)Active immunization:
 One effective way of controlling the spread of
infection is to strengthen the host defenses.
Under certain circumstances this may be
accomplished by active immunization, which
is one of the most powerful and cost-effective
weapons of modern medicine.

a)Active immunization:
 There are some infectious diseases whose control is
solely based on active immunization, e.g., polio,
tetanus, diphtheria and measles. Vaccination against
these diseases is given as a routine during infancy
and early childhood with periodic boosters to
maintain adequate levels of immunity.

a) Active immunization:
 Immunization is a mass means of protecting the
greatest number of people.
 By reducing the number of susceptible in the
community, it augments "herd immunity" making
the infection more difficult to spread.

b. Passive Immunization:
 Short-term expedient useful only when exposure to infection
has just occurred or is imminent within the next few days. The
duration of immunity induced is short and variable (1-6
weeks).
 Process in which antibodies produced in one body (animal or
human) are transferred to another to induce protection against
disease.

b. Passive Immunization:
 Passive immunization has a limited value in the mass control
of disease.
 It is also applied for life saving procedure. Eg: Anti-tetanus
serum.

c. Combined Passive and Active Immunization:
 Passive immunization as well as active immunization
is administered for recent protection by readymade
antibody followed by antibodies produced after active
immunization.

c. Combined Passive and Active Immunization:
 In some diseases (e.g., tetanus, diphtheria, rabies)
passive immunization is often undertaken in
conjunction with inactivated vaccine products, to
provide both immediate (but temporary) passive
immunity and slowly developing active immunity.

d. Chemoprophylaxis:
 Chemoprophylaxis implies the protection from, or
prevention of, disease. This may be achieved by
causal prophylaxis, or by clinical prophylaxis :
 Causal prophylaxis implies the complete prevention
of infection by the early elimination of the invading
or migrating causal agent.

d. Chemoprophylaxis:
 Clinical prophylaxis implies the prevention of clinical
symptoms; it does not necessarily mean elimination
of infection.

e. Non-Specific Measures:
 Improvements in the quality of life.
 Nonspecific measures will also include "legislative
measures”
 Community involvement in disease surveillance,
disease control and other public health activities.

Pre test
• Prevention of emergence of risk factor is
a. Tertiary prevention
b. Primary prevention
c. Primordial prevention
d. Secondary prevention
ANS: c

Pre test
• False about Primary prevention is
a)Early diagnosis and treatment
b)Vaccination
c)Environmental sanitation
d)Health promotion
ANS: a

Introduction
The goals of medicine are to promote health,
to preserve health, to restore health when it is
impaired, and to minimize suffering and
distress.
These goals are embodied in the word
“prevention”.

definition
Activities designed to protect patients or other
members of the public from actual or potential health
threats and their harmful consequences.”
OR
 “Prevention is the action aimed at eradicating,
eliminating or minimizing the impact of disease and
disability.

Levels of prevention
4.Tertiary
3.Secondary
2.Primary
1.Primodial

Primordial prevention
a new concept, perceiving special attention in
the prevention of chronic diseases.
Prevention of emergence or development of
risk factors in population groups in which they
have not yet appeared
Primordial prevention begins in childhood.

Primordial prevention
Primordial level is best level of prevention for non-
communicable diseases.
The main intervention in primordial prevention is
through individual and mass education.

Examples of Primordial prevention
National programs and policies on:
 Food and nutrition
 Comprehensive Policies for discourage smoking,
Alcohol & Drugs
A 5 year old child is discouraged from adopting
harmful lifestyles, smoking, etc

Primary prevention
“action taken prior to the onset of disease, which
removes the possibility that a disease will ever
occur”.
It signifies intervention in the pre- pathogenesis phase
of a disease or health problem

Interventions for primary prevention

approaches for the primary prevention
1. Population or mass strategy
• Directed at the whole population irrespective of
individual risk levels
2. High risk strategy
• Aims to bring preventive care to individuals at
special risk.

Examples of primary prevention
Immunization against measles vaccine.
Health education to prevent spread of malaria.
Vitamin A prophylaxis to a child.

Secondary prevention
Defined as the action which halts the progress of a
disease at its incipient stage and prevents
complications.
Attempts to arrest the disease process, restore health
by seeking out unrecognized disease and treating it
before irreversible pathological changes take place,
and reverse communicability of infectious diseases

Secondary prevention
 It protects others in the community from acquiring
the infection and thus provide at once secondary
prevention for the infected ones and primary
prevention for their potential contacts.

Interventions for Secondary prevention
1.Early diagnosis
• Detection of disturbances of homoeostatic and
compensatory mechanism while biochemical,
morphological and functional changes are still
reversible”
2. Treatment
• Shortens period of communicability, reduce mortality
and prevents occurrence of further cases (secondary
cases) or any long term disability.

Examples of Secondary prevention
1.Early diagnosis
• E.g.“screening for disease” for breast cancer (using
mammography) and cervical cancer (using pap smear),
sputum smear exam for AFB
2. Treatment
• E.g. DOTS for TB

Tertiary Prevention
• Disease process has advanced beyond its early stages.
• Defined as all measures available to reduce or limit
impairments and disabilities, minimize suffering
caused by existing departures from good health and to
promote the patients adjustment to irremediable
conditions.

Tertiary Prevention
Intervention in Late Pathogenesis Phase.
When defect and disability are more or less stabilized,
rehabilitation may play a preventable role.

Interventions for Tertiary Prevention
I. Disability limitation
II. Rehabilitation

I. Disability Limitation:
It prevents the transition of disease from impairment
to handicap.
Example: Physiotherapy in Poliomyelitis.

sequence with which a disease turns into a
handicap
The sequence with which a disease turns into a handicap is as
follows:
 Disease: A disease is a particular abnormal condition that
negatively affects the structure or function of part or all of an
organism.
 Impairment: Any loss or abnormality of psychological,
physiological or anatomic structure or function.
.

sequence with which a disease turns into a
handicap …
 Disability: Any restriction or lack of ability to perform an
activity in the manner considered normal for a human being.
 Handicap: Disadvantage for a given individual, resulting from
impairment or disability, that limits or prevents the fulfillment
of a role that is normal for that individual.

sequence of impairement turns into a handicap …
For example:
Event Classification Interpretation
Accident Disease Impairs function of a person
Loss of foot Impairment Loss of anatomical structure in the form of
foot
Cannot walk Disability Walking is a normal routine daily activity of a
human being
Unemployment Handicap Loses out his job because he cannot walk, so
cannot fulfill his role in the society, i.e,
earning for his family members.

For example:
A person who is born blind (the impairment) is unable to
read printed material, which is how most information is
widely disseminated (the disability). If this person is
prevented from attending school or applying for a job
because of this impairment and disability, this is a
handicap.

II. Rehabilitation
Combined and coordinated use of medical,
social, educational, and vocational measures for
training and retraining the individual to the highest
possible level of functional ability.”
Example: Crutches in Poliomyelitis.

reference
Park, K. (2019). Park`s Textbook of Preventive and
Social Medicine. M/s Banarsidas Bhanot publishers.
Gupta, MC, Mahajan, BK. (2013). Mahajan and Gupta
Textbook of Preventive and Social Medicine. Brothers
Medical Publishers (P) Ltd.
Jain, B. (2016). Review of Preventive and Social
Medicine. The Health Sciences Publisher.
Ghimire, B. (2019). A Textbook of Social Medicine.
Jaypee Community Health Nursing. Vidyarthi Pustak
Bhandar.

mcqs
First case which comes to the attention of
investigator is
a) Primary case
b) Secondary case
c) Index case
d) Carrier

mcqs
Victims of sub clinical infection who have developed
carrier state without suffering from overt disease
a) Healthy carrier
b) Incubatory carrier
c) Temporary carrier
d) Convalescent carrier

mcqs
The disease control describes ongoing operation aimed at reducing the
1. Incidence of disease
2. Financial burden to the community
3. Effects of infection
4. Duration of disease and its transmission
Of these statement;
a) 1,2 & 3 are correct
b) 1,3 & 4 are correct
c) 1,2 &4 are correct
d) 1,2,3,4 are correct
ANS: d

mcqs
In iceberg phenomenon of disease presymptomatic
cases are considered
a. Floating tip
b. Waterline
c. Submerged portion
d. What physician sees in community
ANS: c

mcqs
Decrease in the incidence of a disease to a level
where it ceases to be a public health problem
a. Control
b. Elimination
c. Eradication
d. Surveillance
ANS: a

mcqs
Causative agent is present but there is no
transmission is known as:
a. Elimination
b. Control
c. Surveillance
d. Eradication
ANS: a

mcqs
Which of the following is the most logical sequence?
a. Impairment- Disease- Disability- Handicap
b. Disease- Impairment- Disability- Handicap
c. Impairment- Disability- Handicap- Disease
d. Disease- Disability-Impairment- Handicap
ANS: b

mcqs
Continuous scrutiny of the factors that determine the
occurrence and distribution of and disease other condition of
ill health is definition of
a. Diagnosis
b. Surveillance
c. Disease control
d. System analysis
ANS: b

mcqs
Iodine salt supplementation is:
a.Treatment
b.Specific protection
c.Disbility limitation
d.Health promotion
ANS: b

mcqs
All of the following comes under primary prevention
except:
a.Helmets
b.Sputum test for TB
c.Use of condoms
d.Vaccines
ANS: b

mcqs
Floating tip of the ice berg represents
a. Carriers
b. Undiagnosed cases
c. Clinical cases
d. Latent cases
ANS: c

mcqs
Childhood obesity prevention is a type of
a. Primary prevention
b. Secondary prevention
c. Primordial prevention
d. Tertiary prevention
ANS: c

mcqs
Any restriction or lack of ability to perform an
activity in the manner or within the range considered
normal for a human being is called
a. Impairement
b. Handicap
c. Disability
d. Disease
ANS: c

mcqs
False about Primary prevention is
a. Early diagnosis and treatment
b. Vaccination
c. Environmental sanitation
d. Health promotion
ANS: a

mcqs
A village community was given health education to
prevent spread of malaria. Identify the level of
prevention.
a. Primordial
b. Primary prevention
c. Secondary prevention
d. Tertiary prevention
e. ANS: b

Question
A urine strip for sugar detection was employed to
screen diabetics in community. Identify the level of
prevention and mode of intervention.
ANS: Secondary level of prevention
Early Diagnosis mode of intervention

Question
A child coming to Immunization clinic for OPV
Vaccine. Identify the level of prevention and mode of
intervention.
ANS: Primary level of prevention
Specific protection mode of intervention.

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