Pathogens

A is a microorganism that causes a disease. There are four main types of pathogen:

Pathogen	Example in animals	Example in plants
Viruses	HIV potentially leading to AIDS	Tobacco mosaic virus
Bacteria	Salmonella	Agrobacterium
Fungi	Athlete's foot	Black rose spot
Protists	Malaria	Downy mildew

Pathogen	Viruses
Example in animals	HIV potentially leading to AIDS
Example in plants	Tobacco mosaic virus

Pathogen	Bacteria
Example in animals	Salmonella
Example in plants	Agrobacterium

Pathogen	Fungi
Example in animals	Athlete's foot
Example in plants	Black rose spot

Pathogen	Protists
Example in animals	Malaria
Example in plants	Downy mildew

All types of pathogen have a simple life cycle. They infect a host, reproduce themselves or replicate if it is a virus, spread from their and infect other . They also all have structural that make them successful at completing their life cycles, which enable them to cause further disease.

Diseases caused by pathogens are called . This means they can be transferred from one person to another.

All organisms are affected by pathogens. Even bacteria are infected by certain types of virus. Some of these infections can be transferred to organisms of a different species.

Transmission of diseases

can occur in a number of important ways, as shown in the table below.

Type	Examples
Direct contact	This can be sexual contact during intercourse or non-sexual contact, like shaking hands.
Water	Dirty water can transmit many diseases, such as the cholera bacterium.
Air	When a person who is infected by the common cold sneezes, they can spray thousands of tiny droplets containing virus particles to infect others.
Unhygienic food preparation	Undercooked or reheated food can cause bacterial diseases like Escherichia coli which is a cause of food poisoning.
Vector	Any organism that can spread a disease is called a vector. The mosquito spreads the protist causing malaria.

Type	Direct contact
Examples	This can be sexual contact during intercourse or non-sexual contact, like shaking hands.

Type	Water
Examples	Dirty water can transmit many diseases, such as the cholera bacterium.

Type	Air
Examples	When a person who is infected by the common cold sneezes, they can spray thousands of tiny droplets containing virus particles to infect others.

Type	Unhygienic food preparation
Examples	Undercooked or reheated food can cause bacterial diseases like Escherichia coli which is a cause of food poisoning.

Type	Vector
Examples	Any organism that can spread a disease is called a vector. The mosquito spreads the protist causing malaria.

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Monitoring & maintaining health - Communicable diseases - OCR Gateway Pathogens

Pathogens

Transmission of diseases

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