Understanding the chain of infection can help with the
The spread of an Infectious disease
results from the interaction of a
pathogen, a host (patient), and an
environment. Most of these diseases
follow a typical chain of infection that
ends with an infected patient.
The chain of infection is made up of
six different links: pathogen, reservoir, portal of exit, means of transmission,
portal of entry, and the new host. Each link has a unique role in the chain and
each can be interrupted, or ‘broken’, through various means.
ICRA is designed to break the infection chain in multiple places to ensure
The Chain of Infection is principle used in epidemiology to described infectious
A pathogen is a substance that causes a disease, especially a living
Typically the term is used to
describe an infectious agent such as a
causes disease in its
Yeasts, molds, and mushrooms are all types of fungi. Some fungi are useful
blue cheese, and we eat many kinds of mushrooms.
This training will only discuss bacteria, fungi and viruses because these are the
Serious infection or death can occur when mold spores
Serious infection or death can occur
when mold spores are inhaled or
enter the bloodstream. Mold releases
spores that can become airborne
when disturbed by activities such as
maintenance and construction work
and even from air flow! These spores
are easily inhaled and can cause health problems in people who come in contact
Bacteria can cause diseases in people with weakened
Bacteria are single-cell organisms
that can also be helpful or harmful.
We all have many different species
of beneficial bacteria living in our
intestines, which help us digest food.
But other types of bacteria can make
you sick. They can be resistant to
antibiotics and can be easily transmitted through the air, on contaminated
surfaces and from person to person.
Exposure to bacteria can result from any type of contact, including breathing,
can cause diseases in people with weakened immune systems.
Viruses are a type of pathogen.
A virus is a small infectious agent
that replicates only inside the living
cells of their hosts. They can cause
minor illnesses like the common
cold, but some cause life-threatening
infections, such as liver infections
from hepatitis B.
Viruses spread in many ways;
By coughing and sneezing.
ygiene and handwashing can act as effective
via fecal-oral pathways.
Are passed from person to person by contact, or by entering the body in
food or water.
A pathogen is a substance that causes a disease.
NOTES FOR SLIDE 23
Common pathogens that are of
concern in hospitals especially when
disturbed by construction activities
Aspergillus - The most common
Aspergillus is common in the environment.
Aspergillus is in soil, on plants, and
in decomposing plant matter. It is
also in the dust inside buildings,
such as the dust on top of
suspended ceiling tiles. Most people
breathe in aspergillus spores every
day without getting sick. However,
people with weakened immune
systems or lung diseases are at a higher risk of developing health problems due
Common sources (non-construction) of aspergillus in a hospital are:
especially concerning is the use of non-HEPA
Water systems - Water can contain fungi, and water systems may become
species have been recovered from water taps,
Aspergillus can be found growing on damp walls, as a major component
Construction dust can spread infection because of fungi spores sticking to the
dust particles. Fungi spores are like the seeds of plants, except they are smaller
and usually just single-
celled. But unlike seeds, fungi spores aren’t damaged by
drying out, or by extreme temperatures. Some spores are microscopic, and can
spread in the air, or be airborne.