this power point slide consists the important points regarding to infectious diseases control, helps for medical students as well as clinicians to add some values on their level of awareness regarding to communicable diseases.

1. JIGJIGA UNIVERSITY
COLLEGE OF M&HS
DEPARTMENT OF NURSING
COMMUNICABLE DISEASES CONTROLE
GIRUM.S(MSC, MPH)
November, 2022

2. Communicable diseases control
Definition of common terms in ID.
Definition of infectious disease.
Features of infectious diseases.
 Chain of disease transmissions.
 Types of carriers and disease transmission role.
Time Course of Infectious Diseases.
Mode of transmission
Level of diseases prevention
Principles(strategies) of communicable disease control
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3. Definition common terms
Epidemics -occurrence of disease in excess of what is expected in a
limited period.
 Endemic - a disease that is usually present in a population or in an
area at a more or less stable level.
 Sporadic - a disease that does not occur in that population, except at
occasional and irregular intervals
 Outbreak:- Epidemic of;-
shorter duration
covering a more limited area
affecting small proportion of populations.
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4. Cont…..
 Pandemic - an epidemic spread over several countries or continents,
affecting a large number of people.
 Disease - a state of physiological or psychological dysfunction.
 Infection - the entry and development or multiplication of an infectious
agent in the body of man or animal.
 Infestation:- presence of living infectious agent on the exterior surface of
the body.(Arthropods, rodents)
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5. Definition of common terms….
 Infectious:- caused by microbes and can be transmitted to other persons
Infectious agent:- an agent capable of causing infection
Infectivity:- the proportion of exposed persons who become infected.
Pathogenicity:- the proportion of infected persons who develop clinical
disease.
 Virulence:- the proportion of persons with clinical disease who become
severely ill or die.
 Contamination:- the soiling or pollution of inanimate objects or living
material with ;-
harmful,or
potentially infectious or other unwanted materials.
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7. Definition of communicable diseases
 These are illnesses due to specific infectious agents or its toxic
products, which arise through;-
Transmission of that agent, or
Its toxic products from;-
 An infected person,
 Animal or inanimate reservoir to a susceptible host, either
directly or indirectly.
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8. Infectious diseases
 Unique features of communicable disease:
The cause is known(An infectious agent is a necessary cause)
 A case is a risk factor:- Infection in one person can be transmitted to
others
Carriers as a source of infection
 People may be immuned (herd immunity) i.e measles
Usually their is a need for urgency
Preventable measures are effective
Mostly curable
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9. Natural history of infectious disease
• It refers to the progression of a disease process in an
individual over time, in the absence of treatment.
• stages: exposure, infection, infectious disease, and outcome
• Understanding the natural history of a disease is
• an important prerequisite for designing studies that assess the
impact of interventions,
• both chemotherapeutic and environmental, on the initiation and
expression of the condition
• For example, untreated infection with HIV causes a spectrum
of clinical problems beginning at
• the time of seroconversion (primary HIV) and
• terminating with AIDS and usually death.
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10. Natural history cont…..
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11. Classification of infectious diseases
• Based on infectious agent
Bacterial
Fungal
Viral
Protozoan
• Based on pattern of occurrence
Nosocomial infections
Community acquired infections
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12. Cont…
• Based on clinical manifestation
Diarrheal diseases (cholera, shigellosis...)
Febrile illness (malaria, typhoid...)
Respiratory disease(Pneumonia, tuberculosis...)
UTI infections (Upper and lower UTI)
CNS infection(meningitis ,encephalitis)
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13. Classification Cont…..
 Epidemiological classification/based on modes of disease
transmission:
Food borne disease
Water borne disease
Airborne disease
Vector borne disease
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14. MODES OF TRANSMISSION
1. Direct Transmission
 Skin to Skin.
 Mucosa to Mucosa.
 Mucosa to Skin, of the same person or different Person.
Eg:- STD, AIDS, skin and eye infections.
 Droplet Infection:- Direct Projection of a spray of droplets of saliva and
naso-pharyngeal secretions during
• coughing, sneezing or speaking to the surrounding atmosphere.
Eg: Respiratory infections, diphtheria, whooping cough, TB,
Meningococcal meningitis
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15. 12/8/2022 15
Droplet Sprayed into the Air from a Sneeze

16. DIRECT TRANSMISSION…CONT..
 Contact with Soil
Eg: Hookworm larva, Tetanus
 Inoculation into skin or mucosa
Eg: Rabies, infected needles
 Trans-placental (vertical)
Eg: TORCH agents, syphilis, HBV, AIDS
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17. 2. INDIRECT TRANSMISSION
Traditionally 5F’s
Flies
Finger
Fomites
Food
Fluids
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18. INDIRECT TRANSMISSION…CONT
 Vehicle-borne.
 Water
 Food
 Blood, Serum, Plasma
 Tissues and organs
Vector-born
Air-borne.
Fomite-borne:- Inanimate article or substances other than water or
food contaminated by infectious agents
 Unclean hand and finger
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19. Chain of disease transmission
 There are six successive events implicated in the chain of disease
transmission.
Components of Chain of Infection
1. Causative Agent
2. Reservoir host
3. Portal of exit
4. Mode of transmission
5. Portal of entry
6. Susceptible host
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20. Components of Chain of Infection
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Susceptible host
Neonates Diabetics
Immuno-suppression
Cardiopulmonary
disease
Elderly
Infectious agent
Bacteria
Fungi Viruses
Protozoa Reservoir
People
Equipment
Water
Portal of exit
Excretions
Secretions
Droplets Skin
contact
Means of transmission
Bloodborne Airborne
Droplet Common
vehicle Vectorborne
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21. Cont….
1. Infectious agent
An organism that is capable of producing infection or infectious disease
2. Reservoir of infection
• Which is an infectious agent normally lives and multiplies, on which it
depends primarily for survival and where it reproduces itself
Types of reservoirs
 Man
 Pathogens that are specifically adapted to man, (measles, typhoid,
meningococcal meningitis, gonorrhea and syphilis)
 Animals
Some infective agents that affect man have their reservoir in animals
The term “zoonosis” is applied to disease transmission from animals to man
under natural conditions (Bovine TB, Brucellosis, Anthrax, Rabies)
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22. Cont….
• Non-living things as reservoir
 Many of the agents are basically saprophytes living in soil and fully
adapted to live freely in nature
 C. botulinum etiologic agent of Botulism
 C. tetani etiologic agent of Tetanus
 C. welchi etiologic agent of gas gangrene
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23. Cont….
3. Portal of exit (mode of escape from the reservoir):
This is the site through which the agent escapes from the
reservoir. Examples include:
• GIT: typhoid, fever, bacillarydysentery, amoebic dysentery, cholera,
ascariasis, etc.
• Respiratory: tuberculosis, common cold, etc.
• Skin and mucus membranes: Syphilis
4. Mode of transmission (mechanism of transmission of
infection):
• Refers to the mechanisms by which an infectious agent is transferred
from one person to another or from a reservoir to a new host.
• Transmission may be direct or indirect.
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24. 5. Portals of entry:-
The site in which the infectious agent enters to the susceptible host.
Mucus membrane
Skin
Respiratory tract
intravenous lines,
urinary catheters,
wound sites,
open skin lesions, invasive devices.
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25. cont….
• 6. Susceptible host:- Factors that affect the body’s natural ability to fight
infection include:
1. presence of underlying disease (diabetes)
2. immun-compromised status (HIV, chemotherapy treatment)
3. nutritional status
4. age (the very young and the very old)
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26. Cont…..
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27. Secondary driving factors
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28. Secondary driving factors.
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29. Carrier and Its Type
 carrier is an infected person or animal who does not have apparent
clinical disease but is a potential source of infection to others.
A. Healthy or asymptomatic carriers: -
These are persons whose infection remains unapparent.
E.g….. in poliovirus, meningococcus and hepatitis virus infections, there is a
high carrier rate.
B. Incubatory Carriers : These are individuals or persons who excrete the
pathogen during the incubation period.
(i.e. before the onset of symptoms or before the characteristic features of
the disease are manifested).
• E.g. Measles, mumps, chickenpox and hepatitis.
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30. C. Convalescent Carriers: These are those who continue to harbor the
infective agent after recovering from the illness.
• E.g. Diphtheria, Hepatitis B virus.
D. Chronic Carriers: The carrier state persists for a long period of time.
E.g. Hepatitis B virus infection
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31. Cont…..
Carriers commonly transmit disease ,Because ;-
 Asymptomatic;- they do not recognize they are infected and
consequently take no special precautions to prevent transmission.
 Symptomatic;- persons, on the other hand, are usually less likely to
transmit infection widely because:-
their symptoms increase their likelihood of being diagnosed and
treated,
thereby reducing their opportunity for contact with others.
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32. Carrier and time curse of diseases
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33. Levels of Disease Prevention
• It is important for implementing interventions that prevent
infections.
• Involves the interruption or slowing of disease progression
through appropriate intervention.
• Epidemiology plays a central role in disease prevention by
identifying modifiable causes of disease and their risk factors.
Three levels, (Primary, Secondary and Tertiary)
1. Primary prevention
Primary prevention aims to prevent disease or injury before it ever occurs.
The objectives here are to promote health, prevent exposure, and
prevent disease.

34. Primary prevention….cont…
• legislation and enforcement
• to control the use of hazardous products (e.g. asbestos) or
• to mandate safe and healthy practices (e.g. use of seatbelts and
bike helmets)
• Education about healthy and safe habits (e.g. eating well,
exercising regularly, not smoking)
• Immunization against infectious diseases.
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35. Cont…
A. Health promotion (Primordial):
• This consists of general non-specific interventions that enhance health
and the body’s ability to resist disease – including:
• The improvement of socioeconomic status through the provision of
adequately.
• paid jobs,
• education,
• affordable and adequate housing and clothing, etc.
B. Prevention of exposure:
• There are many examples of interventions aimed at this stage,
• Relatively to specific compared to primordial prevention
• the provision of safe and adequate water, of proper excreta disposal,
• Provision of vector control;
• Provision of a safe environment at home

36. Cont…
C. Prevention of disease:
An example of intervention, which acts at this stage, is passive
immunization.
Some times it may be difficult to differentiate interventions in
what form of prevention they involved
Breastfeeding is an example of an intervention which acts at all
three levels of primary prevention.

37. 2. Secondary prevention
• Secondary prevention aims to reduce the impact of a disease or injury that has
already occurred.
• Strategy is early detecting and treating disease or injury as soon as possible.
• The objective is:-
• slow its progress,
• prevent or limit permanent damage.
• encouraging personal strategies to prevent reinjury or recurrence, and
• implementing programs to return people to their original health and function to
prevent long-term problems.
• Examples include:
• Regular exams and screening tests to detect disease in its earliest stages (e.g.
mammograms to detect breast cancer)
• daily, low-dose aspirins and/or diet and exercise programs to prevent further heart
attacks or strokes
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38. Cont…
3. Tertiary prevention
Intervention that acts after permanent damage has set in,
and the objective of tertiary prevention is to limit the
impact of that damage.
The impact can be physical, psychological, social (social
stigma or avoidance by others), and financial.
Strategy at this stage in general is rehabilitative.

39. Principles of communicable diseases control
• The common principles and terms used in the prevention and controls
of diseases are:
Disease control:
It refers to the reduction of incidence and prevalence of communicable
diseases to a level where it can not be a major public health problem.
Disease elimination:
It is the reduction of infection and disease to zero in a defined
geographical area
Disease eradication:
It is a permanent reduction of worldwide incidence to zero, as a result of
deliberate interventions.
Disease extinction:
It is a permanent, worldwide eradication the infectious agent including
from the laboratory.
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40. ID control…cont..
 Control measures are usually directed against the segment in the chain of
infection that is most susceptible to intervention.
• There are three broad areas /strategies of prevention and
control:-
1. Attacking the source (reservoir) of infection. That is to reduce the
number of infective organisms.
This is done by:
a. Treatment of cases and carriers through mass treatment, as in typhoid
fever, schistosomiasis, tuberculosis.
b. Isolation: separation of infected persons for a period of
communicability.
N.B. Isolation is indicated when diseases:
have high mortality and morbidity.
have high infectivity
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41. ID control…cont..
C. Quarantine: limitation of movement of person or animal
who has been exposed to infectious disease for a
maximum incubation period for the disease.
D. Reservoir control: by mass vaccination to cattle and
sheep and killing & burning infected animals (rabies,
anthrax).
E. Active surveillance of contacts
F. Effective reporting system
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42. ID control…cont..
2. Interrupting the chain of transmission
It is control of modes of transmission from reservoir
to the new host.
Environmental sanitation: - e.g for the control of
intestinal parasites
Personal hygiene: - e.g for trachoma and scabies
control.
 Vector control :- e.g mosquito control for malaria
 Disinfection and sterilization: - e.g purification of
potable water, pasteurization of milk.
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43. ID control…cont..
• 3. Reducing host susceptibility:
a. Immunization - to create immunity at individual level & herd
b. Better and improved nutrition
c. Health education
d. Chemoprophylaxis:-malaria, meningitis, tuberculosis
e. Person protection: - face mask, mosquito nets, clothing,
repellents, shoes, etc
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44. Home take assignment
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45. References
•
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CDC lecture note set by Minichil G
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