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What Are Pathogens and How Do They Spread?

7

1

user profile picture

wrenk

23/08/2025

Biology

AQA Biology Communicable Disease

304

23 Aug 2025

2 pages

What Are Pathogens and How Do They Spread?

user profile picture

wrenk

@wrenkitchens

Pathogens are microorganisms that cause communicable diseases in plants and... Show more

Blology Diseases
Pathogens
are microorganisms, enter the body and cause disease.
L> cause communicable diseases (plants + animals).
·BACTERI

Specific Diseases Caused by Different Pathogens

This page discusses several specific diseases caused by different types of pathogens, including viral, fungal, and protist-caused illnesses.

Viral Diseases:

  1. Measles:

    • Spread by droplets in the air
    • Symptoms include red skin rash and fever
    • Can lead to pneumonia or inflammation of the brain (potentially fatal)
    • Prevention through vaccines
  2. HIV (Human Immunodeficiency Virus):

    • Spread through sexual contact or exchange of bodily fluids
    • Initial symptoms resemble flu
    • Attacks immune cells
    • Can be controlled with antiretroviral drugs if caught early
    • If left untreated, leads to AIDS (Acquired Immunodeficiency Syndrome)

Definition: AIDS is the advanced stage of HIV infection where the immune system is severely damaged and unable to fight off other infections.

  1. Tobacco Mosaic Virus (TMV):
    • Affects many plant species
    • Causes a mosaic pattern on leaves, discoloring parts of the plant
    • Reduces photosynthesis, affecting plant growth

Fungal Disease:

Rose Black Spot:

  • Causes purple or black spots on rose plant leaves
  • Affected leaves may turn yellow and drop off
  • Reduces photosynthesis, impacting plant growth
  • Spreads via water or wind
  • Treated with fungicides or by removing affected leaves

Protist Disease:

Malaria:

  • Caused by a protist that completes part of its life cycle inside mosquitoes
  • Mosquitoes act as vectors, transmitting the disease when feeding
  • Symptoms include repeated episodes of fever, potentially fatal
  • Prevention involves reducing mosquito breeding, using insecticides, and mosquito nets

Highlight: Understanding the life cycles and transmission methods of these pathogens is crucial for developing effective prevention and control of viral diseases and other pathogen-caused illnesses.

Blology Diseases
Pathogens
are microorganisms, enter the body and cause disease.
L> cause communicable diseases (plants + animals).
·BACTERI

Pathogens and Their Characteristics

Pathogens are microorganisms that enter the body and cause disease. They are responsible for communicable diseases in both plants and animals. This page discusses the four types of pathogens and their specific characteristics.

Bacteria are very small living cells that reproduce rapidly within the body. They produce toxins that damage cells and tissues, leading to various bacterial infections.

Viruses, such as measles, HIV, and Tobacco Mosaic Virus (TMV), are even smaller than bacteria. They are not cells themselves but reproduce rapidly within the host's body. Viruses live inside cells and replicate using the cell's machinery, eventually causing the cell to burst and release more viruses.

Highlight: Viral replication inside host cells and subsequent cell damage is the primary mechanism of how pathogens cause disease in viral infections.

Protists, like those causing malaria, are single-celled eukaryotes. Some protists are parasites, living on or inside other organisms and causing damage. They are often transferred to the host organism via a vector.

Fungi, such as those causing rose black spot, can be single-celled or made up of hyphae (thread-like structures). Fungal hyphae grow and penetrate human skin or plant surfaces, causing disease. They also produce spores to spread to other organisms.

Vocabulary: A vector is an organism that transmits a disease or parasite from one animal or plant to another.

How can pathogens spread? They can be transmitted through:

  1. Water (contaminated drinking water)
  2. Air (carried as droplets and breathed in)
  3. Direct contact (touching contaminated surfaces)

Example: The common cold virus can spread through airborne droplets when an infected person coughs or sneezes, or by touching surfaces contaminated with the virus and then touching one's face.



We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user

 

Biology

304

23 Aug 2025

2 pages

What Are Pathogens and How Do They Spread?

user profile picture

wrenk

@wrenkitchens

Pathogens are microorganisms that cause communicable diseases in plants and animals. There are four main types of pathogens and diseases they cause: bacteria, viruses, protists, and fungi. Each type has unique characteristics and methods of causing harm to host... Show more

Blology Diseases
Pathogens
are microorganisms, enter the body and cause disease.
L> cause communicable diseases (plants + animals).
·BACTERI

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Specific Diseases Caused by Different Pathogens

This page discusses several specific diseases caused by different types of pathogens, including viral, fungal, and protist-caused illnesses.

Viral Diseases:

  1. Measles:

    • Spread by droplets in the air
    • Symptoms include red skin rash and fever
    • Can lead to pneumonia or inflammation of the brain (potentially fatal)
    • Prevention through vaccines
  2. HIV (Human Immunodeficiency Virus):

    • Spread through sexual contact or exchange of bodily fluids
    • Initial symptoms resemble flu
    • Attacks immune cells
    • Can be controlled with antiretroviral drugs if caught early
    • If left untreated, leads to AIDS (Acquired Immunodeficiency Syndrome)

Definition: AIDS is the advanced stage of HIV infection where the immune system is severely damaged and unable to fight off other infections.

  1. Tobacco Mosaic Virus (TMV):
    • Affects many plant species
    • Causes a mosaic pattern on leaves, discoloring parts of the plant
    • Reduces photosynthesis, affecting plant growth

Fungal Disease:

Rose Black Spot:

  • Causes purple or black spots on rose plant leaves
  • Affected leaves may turn yellow and drop off
  • Reduces photosynthesis, impacting plant growth
  • Spreads via water or wind
  • Treated with fungicides or by removing affected leaves

Protist Disease:

Malaria:

  • Caused by a protist that completes part of its life cycle inside mosquitoes
  • Mosquitoes act as vectors, transmitting the disease when feeding
  • Symptoms include repeated episodes of fever, potentially fatal
  • Prevention involves reducing mosquito breeding, using insecticides, and mosquito nets

Highlight: Understanding the life cycles and transmission methods of these pathogens is crucial for developing effective prevention and control of viral diseases and other pathogen-caused illnesses.

Blology Diseases
Pathogens
are microorganisms, enter the body and cause disease.
L> cause communicable diseases (plants + animals).
·BACTERI

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Pathogens and Their Characteristics

Pathogens are microorganisms that enter the body and cause disease. They are responsible for communicable diseases in both plants and animals. This page discusses the four types of pathogens and their specific characteristics.

Bacteria are very small living cells that reproduce rapidly within the body. They produce toxins that damage cells and tissues, leading to various bacterial infections.

Viruses, such as measles, HIV, and Tobacco Mosaic Virus (TMV), are even smaller than bacteria. They are not cells themselves but reproduce rapidly within the host's body. Viruses live inside cells and replicate using the cell's machinery, eventually causing the cell to burst and release more viruses.

Highlight: Viral replication inside host cells and subsequent cell damage is the primary mechanism of how pathogens cause disease in viral infections.

Protists, like those causing malaria, are single-celled eukaryotes. Some protists are parasites, living on or inside other organisms and causing damage. They are often transferred to the host organism via a vector.

Fungi, such as those causing rose black spot, can be single-celled or made up of hyphae (thread-like structures). Fungal hyphae grow and penetrate human skin or plant surfaces, causing disease. They also produce spores to spread to other organisms.

Vocabulary: A vector is an organism that transmits a disease or parasite from one animal or plant to another.

How can pathogens spread? They can be transmitted through:

  1. Water (contaminated drinking water)
  2. Air (carried as droplets and breathed in)
  3. Direct contact (touching contaminated surfaces)

Example: The common cold virus can spread through airborne droplets when an infected person coughs or sneezes, or by touching surfaces contaminated with the virus and then touching one's face.

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user