Communicable Disease
Pathogens
- Pathogens are microorganisms that enter the body and cause communicable diseases for both plants and
animals. They can be bacteria, viruses, protists or fungi.
1. Bacteria - They are very small cells, which can reproduce rapidly inside your body. They can make you feel ill by
producing toxins that damage your cells and tissues.
2. Viruses - They aren’t cells, but are tiny and can reproduce rapidly inside your body. They live inside your cells and
replicate themselves using the cells’ machinery to produce many copies of themselves. The cell will
eventually burst, releasing all the new viruses and the cell damage will make you feel ill.
3. Protists - They’re all eukaryotes and most are single-celled, some are parasites which live on or inside
other organisms and can cause them damage. They are often transferred by a vector, which doesn’t get
the disease itself e.g. an insect that carries the protist.
4. Fungi - Some are single-celled, others have a body made up of hyphae (thread-like structures), which can
grow and penetrate human skin and the surface of plants, causing diseases. The hyphae can produce
spores, which can spread to other plants and animals.
Pathogens can be Spread in Different Ways
1. Water - Some can be picked up by drinking/bathing in dirty water, e.g. cholera is a bacterial infection that’s spread by drinking
water contaminated with the diarrhea of other sufferers.
2. Air - Pathogens can be carried in the air and breathed in, some airborne pathogens are carried in droplets in the air that are
produced from sneezes/coughs like the influenza virus that causes flu.
3. Direct Contact - Some pathogens can be picked up by touching contaminated surfaces (including skin), e.g. athlete’s foot is a
fungus which makes skin itch and flake off, most commonly spread by touching the same things as an infected person like towels,
shower floors.
Viral and Fungal Diseases
Measles, HIV and TMV are Viral Diseases
1. Measles - it’s spread by droplets from an infected person’s sneeze/cough, the infected develop a red skin rash and show fever signs.
It can be very serious/fatal, if there are complications, e.g. it can sometimes lead to pneumonia (a lung infection) or a brain
infection called encephalitis. Most people are vaccinated against it when they’re young.
2. HIV - it’s a virus spread by sexual contact or by exchanging bodily fluids like blood, which can happen when people share needles
when taking drugs. It initially causes flu-like symptoms for a few weeks, then the infected doesn’t experience symptoms for many
years. During this time it can be controlled with antiretroviral drugs, which stop the virus replicating. The virus attacks the
immune cells, and if the body’s immune system is badly damaged, it can’t cope with other infections or cancers. At this stage the
virus is known as late stage HIV infection or AIDS.
3. Tobacco Mosaic Virus - it’s a virus that affects many species of plants, e.g. tomatoes and causes a mosaic pattern on the plants’
leaves - parts of the leaves become discoloured. The discoloration means the plants cannot photosynthesise as well, so the virus
affects growth.
Rose Black Spot is a Fungal Disease
- Athlete's Foot - spread via contact, mild fungal condition causes irritation of skin
- Rose Black Spot is a fungus that causes purple/black spots to develop on the leaves of rose plants - the leaves can turn yellow and
drop off, leading to less photosynthesis, so the plant doesn’t grow well. It spreads through the environment in water or by wind.
Gardeners treat it with fungicides and by stripping the plant of its affected leaves, which are then destroyed to ensure the fungus
can’t spread.
Protist and Bacterial Diseases
Malaria is caused by a Protist
- Part of a malarial protist’s life cycle takes place inside a mosquito, which are vectors that pick up the protist when they feed on an
infected animal. Everytime it feeds on another animal, it infects it by inserting the protist into the animal’s blood vessels. Malaria
causes repeating episodes of fever, and can be fatal. People can be protected using insecticides and mosquito nets.
Salmonella and Gonorrhea are 2 Bacterial Diseases
1. Salmonella - it’s a type of bacteria that causes food poisoning, and symptoms include fever, stomach cramps, vomiting and
diarrhoea, which are caused by the toxins the bacteria produces. You can get Salmonella food poisoning by eating contaminated
, food, e.g. eating chicken that had the disease when it was alive, or food that’s been contaminated by being prepared in unhygienic
conditions.
2. Gonorrhoea - it’s an STD, so is passed by sexual contact, e.g. having unprotected sex. It’s caused by bacteria, and a person infected
will feel pain when they urinate, or another symptom is a thick yellow/green discharge from the vagina or penis. It was originally
treated with Penicillin (an antibiotic), but this has become trickier now as the bacterial strains have become more resistant to it. To
prevent the spread, people can be treated with antibiotics and should use barrier methods of contraception, e.g. condoms.
Preventing Disease
The Spread of Disease can be Reduced or Prevented
1. Being Hygienic - using simple hygiene measures, like washing your hands before preparing food or after you’ve sneezed, can stop
you infecting another person.
2. Destroying Vectors - By getting rid of vectors (insects that can be killed using insecticides or by destroying their habitat so they
can’t breed), you stop the disease getting passed on. Malaria spread can be reduced by stopping mosquitoes breeding.
3. Isolating Infected Individuals - isolating someone with a communicable disease, prevents them from passing it on to anyone else.
4. Vaccination - vaccinating people/animals against communicable disease means they can’t develop the infection and pass it on to
someone else, e.g. most poultry in the UK are vaccinated against Salmonella to control the spread of the disease.
Fighting Disease
● The trachea and bronchi secrete
mucus to trap pathogens.
● They are also lined with cilia.
These are hair-like structures, which waft
the mucus up to the back of the throat
where it can be swallowed
● The skin acts as a barrier to
pathogens. It also secretes antimicrobial
substances which kil pathogens
The most important part of your immune system is the white blood cells. They travel around in your body and crawl into every part of you,
patrolling for microbes. How they attack:
They have a nucleus, which can vary in shape from one sort of white blood cell to the next.
There are 3 main methods of attacking microbes:
1. Produce Antitoxins
Pathogens
- Pathogens are microorganisms that enter the body and cause communicable diseases for both plants and
animals. They can be bacteria, viruses, protists or fungi.
1. Bacteria - They are very small cells, which can reproduce rapidly inside your body. They can make you feel ill by
producing toxins that damage your cells and tissues.
2. Viruses - They aren’t cells, but are tiny and can reproduce rapidly inside your body. They live inside your cells and
replicate themselves using the cells’ machinery to produce many copies of themselves. The cell will
eventually burst, releasing all the new viruses and the cell damage will make you feel ill.
3. Protists - They’re all eukaryotes and most are single-celled, some are parasites which live on or inside
other organisms and can cause them damage. They are often transferred by a vector, which doesn’t get
the disease itself e.g. an insect that carries the protist.
4. Fungi - Some are single-celled, others have a body made up of hyphae (thread-like structures), which can
grow and penetrate human skin and the surface of plants, causing diseases. The hyphae can produce
spores, which can spread to other plants and animals.
Pathogens can be Spread in Different Ways
1. Water - Some can be picked up by drinking/bathing in dirty water, e.g. cholera is a bacterial infection that’s spread by drinking
water contaminated with the diarrhea of other sufferers.
2. Air - Pathogens can be carried in the air and breathed in, some airborne pathogens are carried in droplets in the air that are
produced from sneezes/coughs like the influenza virus that causes flu.
3. Direct Contact - Some pathogens can be picked up by touching contaminated surfaces (including skin), e.g. athlete’s foot is a
fungus which makes skin itch and flake off, most commonly spread by touching the same things as an infected person like towels,
shower floors.
Viral and Fungal Diseases
Measles, HIV and TMV are Viral Diseases
1. Measles - it’s spread by droplets from an infected person’s sneeze/cough, the infected develop a red skin rash and show fever signs.
It can be very serious/fatal, if there are complications, e.g. it can sometimes lead to pneumonia (a lung infection) or a brain
infection called encephalitis. Most people are vaccinated against it when they’re young.
2. HIV - it’s a virus spread by sexual contact or by exchanging bodily fluids like blood, which can happen when people share needles
when taking drugs. It initially causes flu-like symptoms for a few weeks, then the infected doesn’t experience symptoms for many
years. During this time it can be controlled with antiretroviral drugs, which stop the virus replicating. The virus attacks the
immune cells, and if the body’s immune system is badly damaged, it can’t cope with other infections or cancers. At this stage the
virus is known as late stage HIV infection or AIDS.
3. Tobacco Mosaic Virus - it’s a virus that affects many species of plants, e.g. tomatoes and causes a mosaic pattern on the plants’
leaves - parts of the leaves become discoloured. The discoloration means the plants cannot photosynthesise as well, so the virus
affects growth.
Rose Black Spot is a Fungal Disease
- Athlete's Foot - spread via contact, mild fungal condition causes irritation of skin
- Rose Black Spot is a fungus that causes purple/black spots to develop on the leaves of rose plants - the leaves can turn yellow and
drop off, leading to less photosynthesis, so the plant doesn’t grow well. It spreads through the environment in water or by wind.
Gardeners treat it with fungicides and by stripping the plant of its affected leaves, which are then destroyed to ensure the fungus
can’t spread.
Protist and Bacterial Diseases
Malaria is caused by a Protist
- Part of a malarial protist’s life cycle takes place inside a mosquito, which are vectors that pick up the protist when they feed on an
infected animal. Everytime it feeds on another animal, it infects it by inserting the protist into the animal’s blood vessels. Malaria
causes repeating episodes of fever, and can be fatal. People can be protected using insecticides and mosquito nets.
Salmonella and Gonorrhea are 2 Bacterial Diseases
1. Salmonella - it’s a type of bacteria that causes food poisoning, and symptoms include fever, stomach cramps, vomiting and
diarrhoea, which are caused by the toxins the bacteria produces. You can get Salmonella food poisoning by eating contaminated
, food, e.g. eating chicken that had the disease when it was alive, or food that’s been contaminated by being prepared in unhygienic
conditions.
2. Gonorrhoea - it’s an STD, so is passed by sexual contact, e.g. having unprotected sex. It’s caused by bacteria, and a person infected
will feel pain when they urinate, or another symptom is a thick yellow/green discharge from the vagina or penis. It was originally
treated with Penicillin (an antibiotic), but this has become trickier now as the bacterial strains have become more resistant to it. To
prevent the spread, people can be treated with antibiotics and should use barrier methods of contraception, e.g. condoms.
Preventing Disease
The Spread of Disease can be Reduced or Prevented
1. Being Hygienic - using simple hygiene measures, like washing your hands before preparing food or after you’ve sneezed, can stop
you infecting another person.
2. Destroying Vectors - By getting rid of vectors (insects that can be killed using insecticides or by destroying their habitat so they
can’t breed), you stop the disease getting passed on. Malaria spread can be reduced by stopping mosquitoes breeding.
3. Isolating Infected Individuals - isolating someone with a communicable disease, prevents them from passing it on to anyone else.
4. Vaccination - vaccinating people/animals against communicable disease means they can’t develop the infection and pass it on to
someone else, e.g. most poultry in the UK are vaccinated against Salmonella to control the spread of the disease.
Fighting Disease
● The trachea and bronchi secrete
mucus to trap pathogens.
● They are also lined with cilia.
These are hair-like structures, which waft
the mucus up to the back of the throat
where it can be swallowed
● The skin acts as a barrier to
pathogens. It also secretes antimicrobial
substances which kil pathogens
The most important part of your immune system is the white blood cells. They travel around in your body and crawl into every part of you,
patrolling for microbes. How they attack:
They have a nucleus, which can vary in shape from one sort of white blood cell to the next.
There are 3 main methods of attacking microbes:
1. Produce Antitoxins
