Transcript Transmission and control of infectious diseases Learning intentions -Describe the different types of pathogens which can cause a disease -Describe how infectious diseases.

Transmission and control of
infectious diseases
Learning intentions
-Describe the different types of pathogens which can cause a disease
-Describe how infectious diseases can be transmitted from person to person.
-Describe good practices to control or reduce the spread of the disease
-Describe the term epidemiology
-Describe the terms sporadic, endemic, epidemic and pandemic
-Describe the control measures which can be used in the event of an epidemic
What are pathogens?
As we have seen, pathogens are agents which
can cause disease.
They can include many different types of
organisms including:
Bacteria
Bacteria are single-celled
organisms and can
cause diseases such
as:
- Cholera
- Typhoid
- Salmonella
- Pneumonia
- Tuberculosis
Viruses
A virus can only survive
outside a host for a very
short time, however they
are responsible for many
diseases;
- AIDS
- Chicken pox
- Influenza
- Herpes
And some cases of cancer,
e.g. Cervical cancer
caused by the Human
papillomavirus (HPV)
Fungus
Fungi are widely used
by humans but some
can cause diseases
like:
- Thrush
- Ringworm
- Athlete’s Foot
Protozoa
Malarial infestation by Plasmodium
http://www.youtube.com/watch?v=OEDhe4M
PEMc
Protozoa are singlecelled organisms
which are typically
mobile. They can
cause:
- Malaria
- Sleeping sickness
- Dysentery
Multicellular parasites
Short clip of tapeworms in situ
http://www.youtube.com/watch?v=JeDD0Hde
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Multicellular parasites
include tapeworms
and hookworms
(pictured).
They can cause
- Anaemia
- Diarrhoea
- Low birth weight
Pathogen Transmission
These pathogens can be transmitted in many
ways:
- Direct physical contact
- Inhaled air
- Indirect physical contact
Pathogen transmission
- Exchanging body fluids
- Faecal-oral route
- Vector organisms
Controlling transmission
Because we know how pathogens are transmitted
we can interrupt it by the following;
- Antisepsis – inhibiting or destroying a
microorganism by sterilising everything that could
carry a pathogen or prevent them reaching
somewhere.
Controlling transmission
Quarantine – isolating the person who is
infected or has been in contact with an
infected person to prevent spreading of the
disease.
The length of the
quarantine is usually
just over the length of
time it usually takes for
someone to display
symptoms after being
infected.
Individual responsibility
Knowing what we do about transmission of
pathogens there are a number of things that can
be used to prevent it;
- Good hygiene – washing hands, brushing teeth,
showering
- Care in sexual health – use of condoms to prevent
sexually transmitted diseases
- Handling and storage of food – washing hands,
keeping raw and cooked food separate and at the
appropriate temperatures.
Community responsibility
Clean water supply – our water is filtered and
chlorinated to prevent growth of
microorganisms… is everyone as lucky?
Safe food webs – for example, milk pasteurisation
(heating at 72o C to kill any microorganisms)
Waste disposal – keeping any refuse collected
regularly and buried or incinerated.
Community responsibility
Control of vectors – Taking care to eradicate any
animals which can carry diseases e.g.
Bubonic plague was caused by bacteria carried by
fleas on rats so being in close proximity to rats
carrying those fleas put you at high risk.
Malaria is caused by a protozoa carried by female
mosquitoes in their saliva. How could you protect
people from this animal vector?
Epidemiology of infectious diseases
Epidemiology is the study of the characteristics
of an infectious disease.
We would look at:
- The location of an initial outbreak
- The pattern and speed of the spread
- The geographical distribution
Patterns of distribution
Sporadic – occurs in scattered or isolated instances with
no connection between them
Endemic – recurs as a regular number of cases in a
particular area
Epidemic – affects an unusually high number of people in
a particular area
Pandemic – occurs as a series of epidemics spreading
across continents or the whole world
What can we hope to do with this?
It is essential to understand how diseases spread so
that we are able to identify appropriate control
measures should an outbreak occur.
Think of the Swine ‘flu outbreak http://www.bbc.co.uk/news/10483218
For overview of methods used to stop the spread of
infection see the following clip
https://www.youtube.com/watch?v=lEzTBzh4NQg