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Course: Fundamentals of Nursing

Topic: The Infectious Process

The Nurses International Community

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COPYRIGHT

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Student Learning Outcomes

Learners will be able to:

Describe the chain of infection
Detail the modes of infection
Identify the types of pathogens

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Definitions

William, n. d

Infection: The invasion and multiplication of organisms such as bacteria, viruses, and parasites that are not normally present within the body
It may:

cause no symptoms and be subclinical
cause symptoms and clinically be apparent

Can be localized or systemic
Bacteria that normally lives within the body is not an infection (eg. E.coli)

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Chain of Infections

Winnipeg Regional Health Authority, 2008

There are 6 components that make up the chain of infection

Infectious agent
Reservoir
Portal of exit
Mode of transmission
Portal of entry
Susceptible host

All the components must be present for a infection to occur

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Infectious Agents

Janeway, 2001

Pathogens: Microorganisms that cause diseases in human are pathogens
Types of pathogens: are mainly 5 types.

Viruses
Bacterias
Fungi
Protozoa
worms

The more virulence, invasiveness, and pathogenicity an organism has, the greater the chance is to cause disease

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Reservoirs

CDC, 2012

This is a place within which microorganism can thrive and reproduce.
Reservoirs can be:

Human beings

Person having an infectious disease
Carrier (incubatory, convalescent)

Animals

Zoonotic (diseases shared between

people and animals)

Rabies, lyme diseases, west nile virus

Inanimate objects

Water, food,soil, feaces (tetanus)

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Human: Diseases that are transmitted from person to person without intermediaries include sexually transmitted diseases, measles, mumps, streptococcal infection, and many respiratory pathogens.

A carrier is a person with an inapparent infection who is capable of transmitting the pathogen to others. Asymptomatic, passive, or healthy carriers are those who never experience symptoms despite being infected.

Incubatory carriers are those who can transmit the agent during the incubation period before clinical illness begins. Convalescent carriers are those who have recovered from their illness but remain capable of transmitting to others.

Animals: Long recognized zoonotic diseases include brucellosis (cows and pigs), anthrax (sheep), plague (rodents), trichinellosis/trichinosis (swine), tularemia (rabbits), and rabies (bats, raccoons, dogs, and other mammals)

Environmental: Many fungal agents, such as those that cause histoplasmosis, live and multiply in the soil. Outbreaks of Legionnaires disease are often traced to water supplies in cooling towers and evaporative condensers, reservoirs for the causative organism Legionella pneumophila

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Portal of Exit

CSC, 2012

This is the means by which a microorganism exits from a reservoir
It can include:

Blood
Respiratory secretions
Urine
Gastrointestinal secretions
Breaks in the skin

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Mode of Transmission

Winnipeg Regional Health Authority, 2008

Mode of transmission:

Is the method or route of transmission by which infectious microorganisms move or are carried to reach a new host

Different modes:

Contact (direct and indirect)
Droplet transmission
Airborne transmission
Vector borne transmission
Common vehicle transmission

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Modes of Transmission

CDC, 2012

An infectious agent is transmitted from the reservoir to a susceptible host in different ways.

Contact

Direct

Indirect

Droplet

Modes of Transmission

Airborne

Vehicleborne

Vectorborne

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Direct Transmission

CDC, 2012

An infectious agent is transfer from a reservoir to a susceptible host by direct contact or droplet spread.
Direct contact occurs through: physical contact between an infected person and a susceptible person.

skin -to-skin contact
kissing (infectious mononucleosis)
sexual intercourse (gonorrhoea, HIV AIDS)
contact with soil
(Hookworm is spread by direct contact with contaminated soil)
contact with body lesions

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Direct Transmission

CDC, 2012

Droplet spread:

is classified as direct because transmission is by direct spread over a few feet, before the droplets fall to the ground.

by coughing, sneezing
Examples: pertussis and meningococcal infections

Some organisms transmitted by this route, especially respiratory viruses, also survive on the objects in the environment. In this case it is also transmitted by indirect contact.

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Droplet Transmission

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Indirect Transmission

CDC, 2012

An infectious organism transmits from a reservoir to contaminated surfaces or to the vectors such as mosquitoes and then to a new host.
Indirect transmission includes:

Airborne transmission
Vehicle-borne transmission
Vector-borne transmission

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Airborne Transmission

Infections occur when microorganisms are carried carried by a dust or droplet nuclei suspended in air to the host
Airborn duct includes:

-Material that has settles on the surfaces and suspended by air currents as well as infectious particles blown from the soil by the wind.
-droplet nuclei are dried residue <5 micron in side.
-droplet nuclei can remain suspended in air for longer period of time and may be blown over greater distance.

Examples :

-Measles, chicken pox

Zoppi, 2020

CDC, 2012

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Airborne Transmission

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Vehicle-borne Transmission

An infectious agent is carried indirectly by inanimate objects.
It includes:

food
water
biological product (Blood)
inanimate objects

(surgical scalpels, handkerchief)

contaminated medical equipment

Example:

Food and water may carry Hepatitis A.
Improperly canned food provide environment for production of botulinum toxin by Clostridium botulinum

(CDC, 2012)

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Vector-borne Transmission

CDC, 2012

An infection transmitted to humans by blood-feeding arthropods, such as mosquitoes, ticks, and fleas
Examples:

-Dengue fever
-Malaria
-Chikungunya
-Plague

Zoonotic diseases:

-transmitted from animal to human

Examples:

Anthrax, listeriosis, rabies

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Critical Thinking Question

A client develops a food poisoning from contaminated food. What is the means of transmission for infectious agent?

Direct contact
Airborne
Vector
Vehicle

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Vector-borne Transmission

CDC, 2012

Types:

Mechanical transmission
Biological transmission

Mechanical transmission:

Carry an infectious agent through mechanical means

Examples:

Flies carrying shigella on their

appendages

Yersinia Pestis in a flea’s gut causes plague

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Vector-borne Transmission

Biological transmission:

infectious agent is carried by the vectors and may support changes in the agents.

Examples:

Plasmodium falciparum causative agent of malaria undergo maturation in intermediate host before it can be transmitted to humans.

CDC, 2012

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Portal of Entry

CDC, 2012

Is the means by which the organisms gains access into the new host to cause an infection.
Examples:

Ingestion
Breathing/ Inhalation
Skin puncture( needle/cut)
Absorption(mucus membranes of Eyes)
Introduction by medical procedures (eg. catheters)

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Susceptible Host

CDC, 2012

A person who is prone to a disease or lacking immunity or physical resistance to overcome invasion by the microorganism.
Some people are more susceptible due to:

low immunity
poor physical resistance
being young or old
malnourished
underlying diseases
people under chemotherapy, steroids
people with open wounds

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Critical Thinking Question

Which client is at higher risk of infection from the following clients?

27 year-old female who is a student
50 year-old male with hypertension
15 year-old male with a fractured hand
30 year-old female with HIV

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References

C. William. MediciNet.(d.n) Medical Definition of Infections.https://www.medicinenet.com/infection/definition.htm

Centers of Diseases Control and Preventions (CDC). (May 2012). Introduction to Epidemiology: Chain of Infections. Principles of Epidemiology in Public Health Practice. https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section10.html

Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; (2001). Infectious agents and how they cause disease. https://www.ncbi.nlm.nih.gov/books/NBK27114/

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References

Winnipeg Regional Health Authority. (2008). The Chain of Infections. https://professionals.wrha.mb.ca/old/extranet/ipc/files/manuals/ltc/ManualPCH_Sec03.pdf

Zoppi, L. (June 16, 2020). Mode of Transmission. News Medical Life Sciences. https://www.news-medical.net/health/Modes-of-Transmission.aspx

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