1. How disease is spread

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. Now try these exercises
Exercise 3 – Cloze exercise
Exercise 4 - Crossword