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How disease is spread
Pathogens
• TB is caused by a bacteria.
• Bacteria are very small microscopic
organisms.
• They are sometimes called microbes.
• Microbes which cause disease are called
pathogens.
• This means disease causing.
• Not all microorganisms are pathogens.
How microbes are transferred
• There are lots of ways
microorganisms are transferred
from one person to another.
• There are two ways these
pathogens are transmitted.
• They are direct and indirect
contact.
Direct contact
• This means that the microbes are passed by
bodily contact.
• There are two methods of direct contact.
• They are horizontal and vertical transmission.
• Horizontal transmission means that the microbes
are passed on by touching, sneezing, kissing
and sexual intercourse.
• Vertical transmission is when the microbes pass
through the placenta from mother to unborn
baby.
Indirect contact
• This means that other humans
are not involved.
• There are two main ways indirect
contact can spread disease.
• They are vehicle-borne and
vector-borne.
• Borne means carried by.
Vehicle-borne
• Vehicle- borne means the microbes are
carried in a physical way.
• Some microbes are carried by the air
• Some diseases can be transmitted in food.
• Water can carry some microorganisms.
• Objects like needles and splinters which
can penetrate the skin can carry disease.
Vector -borne
• This means that the microorganisms are
carried by another animal.
• This is often an insect.
• This might be microorganisms transferred
to your food on the feet of flies.
• Microorganisms can be injected into your
blood by mosquitoes when they bite you.
Now try these exercises
Exercise 3 – Cloze exercise
Exercise 4 - Crossword