Starting with a historic note
Be aware that our bodies
provide a good environment for many microbes to live and multiply at our expense
and can make us ill once they are inside our body.
need to be capable of stopping most microbes from getting in and dealing with any microbes which do get
A simple example of how science
works - cleanliness reduces the incidence of infection!
Appreciate the contribution of Semmelweiss in controlling
the rate of patient infection to solving modern problems with the spread
of infection in hospitals.
Semmelweis worked in Vienna
General Hospital in the 1840s and witnessed large numbers of women dying
after childbirth from a puerperal fever disease.
He thought that the staff of the
hospital were spreading the disease via unwashed hands.
After instructing doctors and
nurses to wash their hands in an antiseptic solution, the mortality rate was
Although Semmelweis didn't
realise it at the time, the antiseptic solution was killing the infecting
Apparently, when he left the
Vienna hospital, the practice of washing hands in the antiseptic solution
was relaxed, and the death rates rose again!
With the advent of new strain of
bacteria today, there is now an even greater need for emphasis on hospital hygiene
than ever before - so, if on a hospital visit, PLEASE WASH YOUR HANDS in the
antiseptic gel provided.
types of dangers are there? Types of pathogens
Communicable/transmissible diseases are those
in which the pathogen is passed from one host to another.
A non-communicable/non-transmissible disease
cannot be passed from one host to another.
Microorganisms or microbes that cause infectious disease are
These pathogens can only be seen under a microscope
and fine details of their structure might only be seen using a
powerful electron microscope.
Bacteria, viruses and fungi can be
harmless or harmful
are very beneficial e.g. in our gut, or they
may reproduce rapidly inside
the body and may produce poisons (toxins) that
make us feel ill.
(i) What is a bacteria?
Bacteria and certain protozoa are very
small cells which can rapidly reproduce by cell division in your body making you feel ill by
damaging your body's cells and producing toxins - poisons produced as a
by-product of the bacteria's cell chemistry.
They can be seen under a light microscope.
Diseases such as tuberculosis, whooping cough and
(ii) What is a virus?
Viruses are NOT
cells and much smaller than bacteria, but damage the cells in which
they reproduce. Viruses replicate by invading a
cell and using the cell's genetic machinery to reproduce themselves ie
copies of the original virus.
The virus 'invaded' cell then
bursts releasing lots of new viruses which go on to invade more healthy
cells. The cell damage makes you feel
ill as your body (temporarily) fights back to make as many good cells as it
can to replace those destroyed by the virus.
The structure of viruses can only be studied using
the power of an electron microscope.
Diseases such as flue, HIV, meningitis, pneumonia
and herpes are caused by viral infections.
Fungi can also be pathogens
and includes microorganisms like yeasts and moulds (so don't eat mouldy
Athletes foot and ringworm are caused by a fungus.
How do our bodies
defences work to counteract pathogens?
The body has two different
types of barriers to protect itself against pathogens - bacterium, virus or
Our body has physical and chemical
adaptations for protecting itself
You may well ask, where do the
pathogens come from?
They are all around us, but
hopefully in very low concentration!
They can be in the air, water or
Pathogens can enter the body
through an accidental cut or graze of the skin.
Bacteria and fungi can be in
contaminated food and so ingested.
Bacteria and viruses,
unfortunately, are readily transmitted by humans!
When we cough or sneeze we spray
into the air thousands of tiny moisture droplets, which may contain
pathogens like bacteria or viruses, which we inadvertently breathe
in. That is why, if at all possible, you should take care to cough
or sneeze into a tissue and dispose of it carefully in a bin.
Microbes will try to enter through any openings in