Which types of pathogens causes communicable
bacteria, fungi, viruses, protists
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INDEX of notes on communicable diseases
(2) Which types
of pathogens causes communicable
The spreading, prevention and treatment of pathogens including:
bacteria - chlamydia, salmonella, tuberculosis,
viruses - HIV, leading to AIDS, colds, flue and human papilloma
fungi - athletes foot and potato blight
Communicable diseases are caused by
pathogens - types of
microorganisms that enter an organism e.g. your body, and cause disease.
Pathogens can infect and cause diseases in both plants and animals,
spread communicable diseases from one organism to another.
Types of pathogen that cause
Bacteria are very
small cells, compared to your own body cells, which can rapidly reproduce by cell division in your body.
They make you feel ill by
damaging your body's cells and tissues and producing toxins - poisons produced as a
by-product of the bacteria's cell chemistry that can damage your cells
You should note that many bacteria are
harmless and some are useful and some essential for a
healthy body. Bacterial biochemistry makes cheese and yoghurt.
Bacteria break down waste and they are very involved in the
digestion of food, absorption of essential nutrients and are
much needed for a healthy gut. There are 300-500 types of
bacteria in your gut that work for your benefit along with
viruses and fungi.
Unfortunately some bacteria are harmful
pathogens to both plants and animals.
Viruses (See also
Viruses - structure, reproduction and cell destruction)
Viruses are NOT
cells, they are much smaller than bacteria and damage the cells in which
Viruses rapidly replicate by invading a
cell and using the cell's genetic machinery to reproduce themselves i.e.
copies of the original virus.
The virus 'invaded' cell then
bursts releasing lots of new viruses to go and invade other cells.
The cell damage makes you feel
ill as your body fights back to make as many good cells as it
can, to replace those destroyed by the virus.
Protists are all eukaryotes,
and there are many types and sizes of them.
Some eukaryotic protists are parasites and live on or inside the 'host'
organism causing some kind of damage.
They are usually transferred to an organism by a vector
which isn't affected by the disease itself e.g. an insect
carrying protist e.g. malaria is caused by an insect (e.g.
mosquito) that carries the protist.
Fungi can be single celled or
others have a 'body' consisting of multi-celled
thread-like structure called hyphae.
Hyphae can grow and penetrate human skin and the
surface of plants causing damage.
Hyphae can produce spores that spread to other plants
Athlete's foot is a fungus which makes skin itch and
It is most commonly spreading by a person coming into contact
with a surface touched by an infected person e.g. shower floors or
- parasites - some nasty species
Helminths are a type of parasitic worm
that can get inside your body e.g. tapeworms, flukes, and
roundworms. Helminthiasis, also known as worm infection, is any
macroparasitic disease of humans and other animals in which a
part of the body is infected with parasitic worms, known as
Soil-transmitted helminthiases are responsible for
parasitic infections in as much as a quarter of the human
population worldwide. They can cause damage to the intestine
wall, inflammation, damage organs such as the skin, lungs and
live and also cause neurological problems.
Trichinosis is a disease caused by
trichinae helminth, typically from infected meat,
characterized by digestive disturbance, fever, and muscular
Ironically, it is thought that
infection by trichinae may reduce the development of some
autoimmune diseases like Crohn's disease.
Autoimmune diseases are diseases
caused by the body's immune system treating its own cells as
if they are foreign and attacking them - a sort of
How do we become infected with a
pathogen (microorganisms or viruses)?
There are many ways in which we, as humans,
can become infected with a pathogen e.g.
Pathogen entering our body through the
skin when bitten by an insect or using an infected needle.
Sexually transmitted disease, when the
pathogen is transferred in sexual activity - through contact of
the fluids from
infected reproductive organs.
(A sexually transmitted infection can be defined as an
infection that is transmitted via body fluids through sexual
Pathogens breathed in through nose or
mouth - aerosol droplets from somebody coughing.
Pathogens taken in through the mouth
contained in contaminated food or drink (polluted water).
Pathogens on a contaminated surface e.g. lack of kitchen
cleanliness or careful personal hygiene,
A brief note on symptoms of
human infection (just some preliminary ideas)
The activity of the pathogen produces
characteristic symptoms which arise from typically two situations.
(a) Reproducing bacteria produce toxins that
are harmful to tissues and makes us feel unwell.
(b) Viruses invade cells and reproduce inside
them, damaging them and killing them - this puts your immune system
and healthy cell reproduction under strain.
These lead to having e.g. a feverish high
temperature, nausea, headaches and rashes on your skin.
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