INFECTION :
The word
“infection “ means something different
from “ disease,” although the two terms sometimes are confused. Disease is a
general word that describes any
abnormality of the human condition or
something that interferes with the normal ,healthy functioning of the
body. Diseases include infection and
infestation , among others. Infection is a term that refers. Specifically to
any abnormal condition caused by a microbe, such as a bacterium ,virus, or
parasite , that has invaded another
organism (like a human )and interfered with some aspect of its function.
An infestation is similar to an
infection.it refer to any abnormal condition cause by an organism larger than a
microbe , such as an insect, louse or worm. the phrase “infectious diseases “
is used to refer to both infections
,regardless of the severity of the condition. An infection beneath a fingernail
and a serious case of hepatitis –C both
are considered infectious diseases.
(AINFECTION
CONTROL:
infection
prevention and control measures aim to ensure the production of those who might
be vulnerable to acquiring an infection both in the general community and while
receiving care due to health problems, in a range of setting . the basic
principle of infection prevention and control is hygiene
·
infection
control is the discipline concerned with
preventing nosocomial or health car-associated infection, a practical (rather
than academic ) sub discipline of epidemiology .
·
It is an
essential, though often under recognized and under supported , part of the infrastructure of health care.
·
Infection
control address factors to the spread
of infections infection within the
health the care setting ( whether patient to patient from patient of staff and from
staff to patients to staff and from staff
to patients, or among –staff) including prevention (via hand hygiene /hand
washing, cleaning /disinfection /sterilization, vaccination, surveillance
),monitoring/investigation of demonstrated or suspected spread of infection
within a particular healthy care setting (surveillance and outbreak
investigation ), and management (interruption of outbreak).
It is on this basis that the common title
being adopted within health care is “infection prevention and control”
1.Nature of infection
:
Infection is invasion of an organism’s body by tissues
by diseases causing agent , their
multiplication ,and the reaction of host tissues to these organism and the
toxins they produce. Infectious
diseases, also known as transmissible diseases,
or communicable diseases,
comprise clinically evident illness(i.e.
chart eristic medical signs and symptoms diseases) resulting from the
infection, presence and growth of pathogenic biological agents in an individual
host organism.
Infection are caused by
infectious agent such s viruses, viroid’s and prions, micro-organisms such as
bacteria, nematodes such as round worms and pinworms arthropods such as ticks,
mites fleas and lice, fungi such as ringworms, and other macro parasites such
as tapeworms.
2. Chain of infection Transmission :
Infectious disease result from
the interaction of an agent , a host, and an environment. most of these
diseases follow a typical chain of infection starting with a reservoir that
contains pathogen and ending with an
infected host. Under standing the chain of infection can help with both the
prevention and treatment of infectious diseases
The chain of Infection :
Definition :
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 hot.
Each link has a unique role in the chain
and each can be interrupted, or ‘broken ‘, through various means.
1. Infectious
Agents/The Pathogen :
·
This is the
disease causing organism.
·
For many illness
and diseases this is a virus or bacterium.
·
In order to
break this link, various methods can be us, including the pasteurization of milk, the chlorination
of drinking water , or the use of disinfectants.
2. The
Reservoir :
·
This is the
natural environment that the pathogen requires for survival.
·
Reservoirs can
be a person , an animal, or an
environment component ,such as
soil or water,
·
This link can be
broken through medical treatment and testing, insect and rodent eradication ,
or quarantine.
3.
The portal of Exit :
·
This link is
needed for the pathogen to leave the reservoir.
·
If the reservoir
is a human, then the portal of exit may be saliva , mucous membranes, feces,
blood, or nose or throat discharges.
·
By using barrier
method , such as condoms or masks, or covering the mouth while coughing , this
link can be broken.
4. The means
of Transmission :
·
The pathogen can
be transmitted either directly or indirectly.
·
Direct
transmission requires close association with the infected host, but not
necessarily physical contact.
·
Indirect
transmission required a vector, such as n animal or insect.
·
The link can be
broken through hand washing, safe sex practices, or avoiding contact with
infected individuals.
5. The portal
of entry;
·
Entry of the
pathogen can take place in one of three ways: penetration, inhalation , or
ingestion
·
The level and
severity of an infection may depend on the depth of penetration.
·
Similar to the
portal of exit, barrier methods, such as condoms or masks , can be used to
break this link , along with other methods, such as insect repellants.
6. The new
host :
·
Once in the new
host , various factors influences the severity of infection , including the
strength of the immune system and the reproductive rate of the pathogen.
·
Immunization ,
health promotion , and medical treatment
can be used to break this link in the chain.
Example
:
·
An example of
illness resulting from the chain of infection is the common cold.
·
In this case,
the pathogen is often referred to as rhinovirus.
·
The reservoir is
the another person carrying this virus,
who then propels the virus into the air via a portal of exit, such as a
cough or sneeze.
·
The route of
transmission is direct to the new host, which takes place through inhalation
(the portal of entry) of the virus
Six
Elements of infection :
There are six elements in the cycle of
infection, and all six must be present before the transmission of infection can
take place .
|
Elements
in the cycle of infection |
Explanation |
Common
examples |
|
Infectious
agents |
When
germs enter the body, they can cause
illness |
·
Bacteria , virus, fungi, protozoa |
|
Reservoir
|
Where
germs normally live and multiply |
·
Humans , ·
contaminated food , water , toys ,
sports equipment’s. ·
insects animals , soil |
|
Portal
of exit |
How
germs leave in the body |
·
Respiratory tract, ·
intestinal tract, ·
open wounds ·
urinary / genitourinary tract ·
blood and body fluids |
|
Transmission
|
How
germs are spread. Refers to next page for a detailed explanation oh how
infections spread. |
·
Direct physical contact ·
Respiratory droplet ·
Stool( fecal – oral route ) ·
Contact with blood / body fluids ·
Indirect contact ·
Needle stick injury ·
Ingestion of contaminated food and
water ·
Contaminated dust particles ·
Contaminated objects ·
Insects/ animals ·
|
|
Portal
of entry |
How
germs enter the body |
·
Respiratory tract ·
Intestinal tract ·
Urinary / genitourinary tract ·
Open wounds ·
Mucus membrane , e.g. eye , mouth |
|
Susceptible
host |
A
person who gets an infection because he / she is unable to successfully fight
the infection |
·
Infants , elderly and debilitated ·
Persons who are ill ·
Children who are not fully immunized or have
underdeveloped immune system ·
Person taking certain drugs that lower their
defences against germs ·
Persons with underlying disease conditions
that lower their defence against other
germs. |
3. Defence Against infection
Natural and Acquired :
Infection
are the most common cause of human disease. They range from the common cold to
debilitating condition like chronic
hepatitis to life –threating disease such as AIDS. Disease-causing microbes
(pathogens) attempting to get into the body must first move past the body’s
external armour, usually the skin or
cells lining the body’s internal passageways.
·
The skin provides an
imposing barrier to invading microbes. It is generally penetrable only through
cuts or tiny abrasions.
·
The digestive and
respiratory tracts both portals of entry for
a number of microbes-also have
their own level of protection.
·
Microbes entering the
nose often cause the nasal surfaces to secrete more protective mucus, and
attempts to enter the nose or lungs can trigger a sneeze or cough reflex to
force microbial invars out of the respiratory passageways.
·
The microbes survive the body’s front-line defenses, they
still have to find a way through the wall of the digestive, respiratory , or
urogenital passage ways to the underlying cell.
·
These passageways are
lined with tightly packed epithelial cell covered in a layer of mucus ,
effectively blocking into deeper cell layers.
Acquired Defences :
The immune response involves specific body
responses to an invading foreign protein, such as bacterial or in some cases ,
to the body’s own proteins.
·
Inflammatory
Response: The inflammatory response is a
protective mechanism that eliminates the invading pathogen and allows for
tissue repair to occur.
·
Inflammation Helps the
body to neutralize, control or eliminate the offending agent and to prepare the
site for repair .
·
The cardinal signs of
acute infection are redness, heat, swelling, pain and loss of function and
usually appear at the site of injury or inflammation.
·
Components of
inflammatory process.
(a) Vascular
stage.
(b) Cellular
stage.
(a)
Vascular
Stage : In
vascular stag small blood vessel constrict in the area followed by vasodilation
of arterioles and venules that supply the area. This increase in blood flow
results in redness and heat in the area . histamine also is released leading to
an increased permeability of vesls, which allow protein-rich fluid to pour into
the area. At this point ,swelling pain and loss of function can occur. The
foreign material is called an antigen and the body commonly responds to
the antigen by producing an antibody .
this antigen antibody reaction is also known as humoral immunity.
(b)
Cellular
stage :
It also helps the body defends against
invaders is a cell mediated defense or cellular immunity. It involves an
increase in the number of lymphocytes that destroy or react ith cell the body
recognizes as harmful.
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