Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. Diseases can be classified into two groups:

  1. Communicable: meaning that the disease can be transferred from one organism to another
  2. Non-Communicable: meaning that the diseases cannot be transferred between organisms.

If an individual has a diseases, they are more susceptible to contract other diseases because different types of diseases can interact with each other.

For example, if someone had a weak immune system, then the individual is more likely to suffer from infectious diseases.

A lot of people with physical health issues will end up developing mental health issues too.

A pathogen is a disease-causing organism, including viruses, bacteria, fungi and protists.

Communicable Infections

Cholera is a type of bacterial infection that can be found in dirty water, or in contaminated food. If someone has drank dirty water with cholera, or eaten some contaminated food, they may experience diarrhoea, vomiting and stomach cramps.The individual may then become dehydrated, and the body can go into shock.

Tuberculosis is a bacterial infection that infects the lungs. It spreads through the air, as an individual with tuberculosis may cough, and the tiny droplets will contaminate someone else. If an individual has tuberculosis, they may cough so much that they may cough out blood. They may experience weight loss as they lose their appetite, have a high temperature and feel fatigue.

Chalara ash dieback is a fungal infection that causes leaf loss. New shoots will die easily and bark lesions may also be seen.

Diseases, figure 1

Malaria__ is a __protist, and it is spread by mosquitoes. It causes significant damage to blood and the liver, and is usually found in warmer countries.

Mosquitoes suck the blood from someone that is infected. They will pass the protist to other individuals that they will suck blood from. Mosquitoes themselves do not get ill - they simply pass on the protist to the next person so that they can get infected.

If someone has malaria, they may experience a fever, sweats, chills, headaches, vomiting and diarrhoea.

Diseases, figure 2

HIV is a virus that destroys white blood cells, and leads to the onset of AIDS. It is transmitted through bodily fluids (during unprotected sex, cuts, injection of drugs with needles). Individuals with HIV may firstly experience flu symptoms. When an individual has HIV, their virus starts attacking the individual’s white blood cells.

Stomach ulcers are caused by helicobacter, a type of bacteria that lives in the stomach lining. It is normally transmitted through the saliva. An individual with the infection will have an irritated lining of the stomach, which then stops protecting them from the hydrochloric acid environment in their stomach. Because of this, it will develop ulcers.

When an individual has stomach ulcers, they may experience indigestion, heartburn, and a loss of appetite and weight loss.

Ebola is a __virus __that can cause fevers, headaches, joint and muscle pain and muscle weakness. Individuals may then experience diarrhoea, vomiting, stomach pains and internal bleeding. The virus is usually transmitted through bodily fluids, or it can also be caught from a dead person.

Virus Life Cycle

Viruses can survive outside of their host for long periods.

They will only replicate themselves when they have found a suitable host cell.

They divide and reproduce rapidly through the lytic pathway:

  1. They duplicate their DNA and protein coats
  2. Which is then assembled into new virus particles
  3. This would cause the host cell to burst
  4. This would then infect nearby cells with the virus
  5. The lysogenic pathway then takes place - where phages (other type of virus) can either join their DNA to their host, or it can leave behind small circles of their DNA in the host cell’s cytoplasm
  6. The viral DNA is then copied, and the lytic cycle would begin again

Diseases, figure 1

How is cholera spread?
Your answer should include: Consumption / Contaminated / Food / Water
Explanation: Through the consumption of contaminated food and water.
What are stomach ulcers caused by?
What’s the difference between a non communicable disease and a communicable disease?
Your answer should include: Spread / Between / Organisms
Explanation: A communicable disease can be spread between organisms, whilst a non-communicable disease can’t

Spread & Prevention


How is it spread

How can it be reduced


Contaminated water and food

Filter water, cook food properly



Having a strong immune system

Chalara Ash Dieback


Remove infected areas of the plant



Use of mosquito nets,


Oral transmission

Avoid smoking


Unprotected sex, catching the diseases off a dead person or their possessions

Encourage protected sex