What is health, and what types of pathogen cause communicable disease?
Describe health and the difference between communicable and non-communicable diseases, how having one disease can increase susceptibility to others, the four types of pathogen, and some common infections.
A focused answer to Edexcel GCSE Biology 5.1 to 5.5, covering the WHO definition of health, communicable and non-communicable diseases, how diseases interact, the four pathogen types, and named common infections.
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What this dot point is asking
Edexcel statements 5.1 to 5.5 want you to define health (using the WHO definition), distinguish communicable from non-communicable diseases, explain how having one disease can raise susceptibility to others, describe the four types of pathogen, and name some common infections caused by each.
What is health?
This wider definition matters: a person can be free of infection but still in poor health because of stress, poor mental health or social isolation. Good health depends on diet, exercise, lifestyle and mental well-being, as well as freedom from disease.
Communicable and non-communicable disease
How diseases interact
Diseases do not always act alone. Having one disease can increase the chance of getting another:
- A pathogen that damages the immune system, such as HIV, leaves the body less able to fight off other infections.
- Defects in the immune system mean a person is more likely to suffer from infectious diseases.
- Some long-term infections trigger other illnesses: for example, infection with certain viruses can lead to cancers, and an immune reaction can cause conditions such as allergies.
So one disease can make a person more susceptible to others.
The four types of pathogen
- Viruses are not cells; they reproduce inside host cells and damage them. Examples: measles, HIV, and (in plants) tobacco mosaic virus.
- Bacteria are cells that can reproduce rapidly and may release toxins that damage tissues. Examples: cholera, and Helicobacter (stomach ulcers).
- Fungi can grow on or in the body or on plants. Examples: athlete's foot, and rose black spot in plants.
- Protists are single-celled organisms, often spread by a vector. Example: the protist that causes malaria, spread by mosquitoes.
Try this
Q1. State the WHO definition of health. [1 mark]
- Cue. A state of complete physical, mental and social well-being, not merely the absence of disease.
Q2. Give one difference between a communicable and a non-communicable disease, with an example of each. [2 marks]
- Cue. Communicable can be spread and is caused by a pathogen (e.g. measles); non-communicable cannot be spread (e.g. cancer or type 2 diabetes).
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20194 marksDescribe the four types of pathogen and give a named disease caused by each.Show worked answer →
A 4-mark describe question rewards each pathogen type with a correct named disease.
- Viruses (e.g. measles, HIV, or tobacco mosaic virus in plants).
- Bacteria (e.g. cholera, or Helicobacter causing stomach ulcers).
- Fungi (e.g. athlete's foot, or rose black spot in plants).
- Protists (e.g. malaria, caused by a protist spread by mosquitoes).
Markers reward all four types correctly matched to a valid disease. Putting a disease under the wrong pathogen (such as calling malaria a bacterial disease) loses marks.
Edexcel 20212 marksExplain why a person with HIV may become more likely to catch other infections.Show worked answer →
A 2-mark explain question rewards the link between one disease and weakened defences.
HIV attacks and weakens the immune system (the white blood cells). With a weaker immune system, the body is less able to defend itself against other pathogens.
This means the person becomes more susceptible to other infections that a healthy immune system would normally fight off. Markers reward the idea that HIV damages the immune system, leading to higher susceptibility to other diseases. Saying HIV simply makes you ill, without the immune-system link, scores less.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Biology (1BI0) specification — Pearson (2016)