How are pathogens - infections spread? The ways in which infectious diseases
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Sub-index of biology notes on communicable diseases
(3) How are pathogens spread?
There many sorts of ways that pathogens can spread.
Pathogens are carried in air currents and breathed in
e.g. fungal spores.
Airborne pathogens are conveyed through the air in water
droplets when we cough or sneeze e.g. the influenza virus
giving us 'flue' or tuberculosis.
When people are crowded together, their
close proximity allows an easy transfer of a communicable
disease from one person to another e.g. coughing out a cold or
contact and body fluids
Pathogens can be picked up by merely touching a contaminated
surface including someone's skin e.g. athlete's foot is a
fungus which makes skin itch and flake off.
It is most
commonly spreading by coming into contact with a surface an
infected person has e.g. shower floors or towels.
Sexually transmitted infections/diseases (STI/STD) are
passed on in sexual activity where bodies are in direct
(A sexually transmitted infection can be defined as
an infection that is transmitted via body fluids through
Ebola can be spread through
contact with infected bodily
fluids of another person.
These include like blood (drug users
sharing needles), vomit, saliva, faeces, breast feeding
milk (mother to child), and sexual activity (contact with semen).
is a good example.
Dirty contaminated water is a common source of pathogens and
should not be drank or bathed in.
Cholera is a bacterial
infection spread by drinking water contaminated with the
diarrhoea of people already infected with the bacteria.
Some pathogens can be carried and
transported by an animal organisms referred to as vectors.
The mosquito is an example of an animal
vector which carries the protist pathogen that causes
plant disease notes - pathogens
in the soil
Pathogens maybe present in food.
Contaminated food may contain the
healthy3comdisease-04.htm bacterium causing food poisoning.
The Helicobacter pylori bacterium
that causes stomach ulcers maybe found in contaminated food or
Keywords, phrases and learning objectives for this part on
how communicable diseases spread
How are pathogens causing communicable diseases
infections spread? ways of transfer by body fluids food animal
vectors air airborne water soil bacteria fungi protists
Be able to
how pathogens are spread, including:
a) in water, including cholera bacterium
You can be infected with a pathogen by
coming into contact with contaminated water - which is why swimming bath
waters are treated to kill bacteria with chlorine or ozone. In poor third
world countries the bacterial infection cholera, which causes diarrhoea and
dehydration, is readily spread in water contaminated with the faeces of
cholera sufferers. It is potentially very serious, particularly for the very
young and the very old and undernourished adults and children in poor third
world countries with poor sanitation.
by food, including Salmonella bacterium infection
If you eat food contaminated with pathogens
the resulting food poisoning effects can be very unpleasant and potentially
very serious, particularly for the very young and the very old and the poor
of the third world. If food is kept too long at the wrong temperature, left
out in the open, or food like meat undercooked, you may be poisoned by the
c) airborne (eg coughing, sneezing), including
influenza virus (causes flue)
If you are suffering from a cough, chest
infection or flue etc. and you don't take precautions with a large
handkerchief or tissue, when you cough or sneeze you blast out into the air
a fine mist of water droplets containing millions of bacteria or viruses.
People around you breathe in you exhaled pathogens and potentially become
infected. Lots of people in a crowded room are great breeding places for
d) by contact, including athlete’s foot fungus
You can be infected with a pathogen just by
touching a contaminated surface with e.g. your hand or foot. A common
example is the spread of athlete's foot, a fungal infection easily spread in
swimming bath surfaces, shower floors, towels i.e. anything an athlete's
foot carrier has been in contact with.
e) by body fluids,
including HIV infection
The HIV virus causes AIDS, a disease that
stops our immune system from functioning properly - you become more
susceptible to infectious diseases than a normal healthy person and the
condition is often fatal in the end, despite the best efforts of anti-viral
drugs. These kinds of pathogens can only be passed on by direct contact with
body fluids from another person e.g. from a HIV carrier's sperm during
sexual intercourse, or some body penetrating situation e.g. using the same
drug needle as a HIV carrier.
f) by animal vectors (animals that spread
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