disease transmission Ramji pandey consultant optometrist

Ppt

1. Disease transmission and Prevention of infection
Ramjipandey

2. Disease Transmission
•Communicable disease are transmitted from source of infection to susceptible
individual in many different ways, depending on infectious agent,portal of entry and
local ecological conditions.
•The mode of transmission of disease may be classified as below-
•1)Direct transmission
•2) Indirect transmission

3. Source: Heymann DL. Control of communicable diseases manual. 19
th
Edition. Washington DC,
USA: American Public Health Association; 2008. 746

10. Infection Transmission
 Mother to Unborn Child
 In utero, perinatal
Direct Contact
Agent transferred from reservoir or host
Person-to-Person
Direct spread of droplets
Animal to Person (e.g., bite)
Mother to Unborn Child
In utero, perinatal
Indirect Contact
Agent transferred indirectly from reservoir or
infected host
Mechanical
Touching an infected inanimate
object then yourself without
thoroughly washing.
Biological
Biological Vector
Intermediate Vector (e.g., flea,
tick)
Airborne (sneeze, cough)
Indirect Contact
Agent transferred indirectly from reservoir or infected host
 Mechanical
 Touching an infected inanimate object then yourself without thoroughly washing.
 Biological
 Biological Vector
 Intermediate Vector (e.g., flea, tick)
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11. Direct contact
Direct contact transmission of pathogens can occur through physical contact.
Many pathogens require contact with a mucous membrane to entDirect contact
transmission of pathogens can occur through physical contact. Many
pathogens require contact with a mucous membrane to enter the body, but the
host may transfer the pathogen from another point of contact (e.g., hand) to a
mucous membrane (e.g., mouth or eye).
er the body, but the host may transfer the pathogen from another point of
contact (e.g., hand) to a mucous membrane (e.g., mouth or eye).

12. Direct contact
When skin or mucus membrane (thin most lining of many parts of the body comes
into When skin or mucus membrane (thin most lining of many parts of the body
comes into contact with the skin or mucus membrane of infected person (cold sores,
head lice, conjunctivitis)
ontact with the skin or mucus membrane of infected person (cold sores, head lice,
conjunctivitis)

13. Indirect transmission
•Airborne
•Vehicles
•Vector-mechanical or biologic
Airborne
Vehicles
Vector-mechanical or biologic
Vehicles
Vector-mechanical or biologic

14. Airborne
Occurs when infectious agent are carried by dust or
droplet nuclei suspended in the air
Airborne Dust includes material that has settled on
surfaces and become resuspendedby air currents
Droplet Nuclei are dried residue of less than 5 microns in
size
•Airborne Dust includes material that has settled on surfaces and
become resuspendedby air currents
•Droplet Nuclei are dried residue of less than 5 microns in size

15. Airborne
Airborne dust and Droplet Nuclei can travel long distances on air currents and
remain suspended in the air for minutes to hours. This particles may be breathed
by other persons. (Chickenpox, Tuberculosis, Measles)

16. vehicles
Indirectly transmit an infectious agent include food,
water, biologic products, and fomites
Fomites are inanimate objects such as handkerchiefs,
beddings, surgical scalpels
•l scalpels

17. vehicles
Food is an important vehicle of transmission for pathogens, especially of
the gastrointestinal and upper respiratory systems. Often these infections
are also spread by the fecal-oral route (Hepatitis A, E)
is an important vehicle of transmission for pathogens, especially of the
gastrointestinal and upper respiratory systems. Often these infections are
also spread by the fecal-oral route (Hepatitis A, E)

18. vehicles
Fomites are nonliving objects that facilitate the indirect transmission of
pathogens. Contaminated doorknobs, towels, and syringes are all common
examples of fomites.
oorknobs, towels, and syringes are all common examples of fomites.

19. Vector-biologic transmission
Mosquitoes through biting the host create a wound that
transmits Malaria and other diseases
Ticks can transmit Lyme Disease
Rabid animals like Monkey, Dog and Cats may transmit
rabies virus by means of bite
•Lyme Disease
•Rabid animals like Monkey, Dog and Cats may transmit rabies
virus by means of bite

20. vectors
(a) A mechanical vector carries a pathogen on its body from one
host to another, not as an infection. (b) A biological vector carries
a pathogen from one host to another after becoming infected
itself.

21. Epidemiologic Factors
•There are 3 main
factors related to
development of HAIs
»Host factors
»Agent factors
»Environmental
factors
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22. Host Factors
•Coma
•HIV infection
•Malignancies
•Diabetes mellitus
•Severe malnutrition
•Circulatory impairment
•Open wound or trauma
•Bronchopulmonarydisease
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•Advanced age or
premature birth
•severe burns and
certain skin diseases
•Chronic obstructive
pulmonary disease
•Immunodeficiency (due
to drug, or irradiation)

23. Agent Factors
•An infectious agent can be bacteria, virus, fungus, or
parasite
•The majority of HAIs are caused by bacteria or viruses
•Two major types of bacteria that cause HAIs
•Gram-positive cocci (e.g., Staphylococciand
Streptococci)
•Gram-negative bacilli (e.g., Acinetobacter,
Pseudomonas, Klebsiella)
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24. Environment Factors
•Extrinsic factors that affect either the
infectious agent or a person’s risk of
exposure to that agent
•Include both the animate and inanimate
environment of patients
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25. Mode of transmission
Portal of entry
Host
Infectious agent
Reservoir
Portal of exit
Chain of Infection -1
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26. Chain of Infection -2
•Infection results from an interaction between an
infectious agent and susceptible host
•The interaction occurs by means of contact
between the agent and the host and is affected by
the environment
•Breaking the chain of infection by interrupting
transmission generally the best way to prevent
HAIs
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27. Infectious Agents
•A pathogen that causes an HAI
•Most important pathogens causing HAI
are Gram-negative bacteria
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28. Reservoir
Definition:
–Place in which an infectious agent can survive but may or may
not multiply
Common reservoirs:
•humans
•animals
•equipment/fomites
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29. Human Reservoirs
Human reservoir: Persons
with acute or subclinical
illness
Carriers
–convalescent carriers
–chronic carriers
–intermittent carriers
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30. Portal of Exit
The path by which an infectious agent leaves the
reservoir
–Respiratory tract
–Genitourinary tract
–Gastrointestinal tract
–Skin/mucous membrane
–Blood
–Transplacental
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31. Modes of Transmission
•A pathogen may be transmitted by a single route or it
can be transmitted in several ways
•Modes of transmission are as follows:
–Contact transmission: direct, indirect-contact, and
droplet
–Airborne transmission
–Vehicle transmission
–Vector-borne transmission
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32. Contact Transmission
Direct contact
•person-to-person spread, actual
physical contact
Indirect contact
•contact with contaminated
intermediate object
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33. Droplet Transmission
•Large droplets generated by an infected
or colonised person during coughing,
sneezing, talking, suctioning, etc.
•Droplets propelled a short distance
<3m
•Droplets deposited on a susceptible
host’s eyes, nasal mucosa or mouth
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34. Airborne Transmission
Droplet nuclei, dust particles
or skin squamescontaining
microorganisms are
transmitted to a susceptible
host by air currents
TB or not TB?
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35. Common Vehicle Transmission
Microorganisms are transmitted to
susceptible hosts from common
items:
–Food
–Water
–Medications
–Devices/equipment
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36. Vector-borne Transmission
Transfer of microorganisms by
insects, flies, rats, or other vermin
Uncommon mode of transmission in
hospitals
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37. Portal of Entry
The path by which an infectious agent enters the
susceptible host
»Respiratory tract
»GU tract
»GI tract
»Skin/mucous membrane
»Parenteral
»Transplacental
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38. Susceptible Host
A person lacking effective
resistance to a particular
microorganism
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40. Bacterial Infections
A single-celled organism.
 Under certain circumstances some can transform into spores.
 Bacteria are larger than viruses and are capable of reproducing on their own.
Beneficial bacteria live in the human gastrointestinal (GI) tract and play an important role in digestion and
immunity.
A single-celled organism.
Under certain circumstances some can transform into spores.
Bacteria are larger than viruses and are capable of reproducing on their own.
Beneficial bacteria live in the human gastrointestinal (GI) tract and play an important
role in digestion and immunity.
Bacteria can infect any area of the body.The disease-causing method can occur in one of two
ways:
Invading host tissues, and
Producing poisons (toxins)
Pneumonia, dermatitis, meningitis, and food poisoning are few examples.
Certain gram-negative bacterium, like E. coli and Salmonella can be present in
uncooked foods.
Bacterial skin infections are usually caused by gram-positive strains
ofStaphylococcusandStreptococcusor other organisms.
Many sexually transmitted diseases (STDs) are caused by harmful bacteria
(Chlamydia, Gonorrhea, Syphilis, Bacterial vaginosis).
Bacteria can infect any area of the body.The disease-causing method can occur in one of two ways:
 Invading host tissues, and
 Producing poisons (toxins)
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41. Prevention and Control Measures Applied to Break
Different Stages of the Infection Chain

42. Measures Directed towards Protecting Portal of
Entry
•Using bed-nets
•Wearing masks and gowns to prevent entry of infected body secretions
or droplets through skin or mucous membranes
•Covering skin and using insect repellents