What causes disease, which pathogens are responsible, and how can the spread of infection be reduced?
The causes of disease, the types of pathogen and example diseases, how pathogens are spread, and the ways the spread of infectious disease can be reduced, including non-communicable diseases and their risk factors.
A focused answer to the WJEC GCSE Biology section 2.8 topic on disease, covering the causes of disease, the four types of pathogen with example diseases, how pathogens are spread, ways to reduce the spread of infection, and non-communicable diseases and their risk factors.
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What this dot point is asking
WJEC wants you to know that disease has several causes, the four types of pathogen with examples, how pathogens spread, ways to reduce the spread of infection, and that some diseases are non-communicable with their own risk factors.
The causes of disease
Not all disease is caused by infection. Disease may be caused by:
- Pathogens (infectious disease).
- Genetic factors inherited from parents.
- Poor nutrition, such as a lack of vitamins or minerals.
- Organ malfunction, where a body part stops working properly.
- Environmental factors, such as harmful chemicals or radiation.
Types of pathogen
A pathogen is a micro-organism that causes disease. There are four main types, each with example diseases.
| Pathogen type | Example disease |
|---|---|
| Virus | Influenza (flu), measles |
| Bacterium | Tuberculosis, food poisoning |
| Fungus | Athlete's foot |
| Protist | Malaria |
How pathogens spread
Pathogens can move from one organism to another by several routes:
- In water, for example through contaminated drinking water.
- In food, for example through undercooked or contaminated food.
- By air, in tiny droplets when an infected person coughs or sneezes.
- By direct contact, including touch and sexual contact.
- By vectors, such as insects that carry a pathogen between hosts.
Reducing the spread of infection
The spread of infectious disease can be reduced in several ways, each matched to a route of transmission:
- Hygiene, such as washing hands and surfaces, reduces direct contact and food spread.
- Safe food preparation, including cooking thoroughly and storing food cold, reduces spread in food.
- Safe sex, including using condoms, reduces spread by direct contact.
- Vaccination protects people so they cannot catch or pass on the disease.
- Isolation of infected people stops them passing the pathogen to others.
Non-communicable disease
Some diseases are non-communicable, meaning they cannot be caught or passed between people. Examples include coronary heart disease, some cancers and Type 2 diabetes.
The risk of non-communicable disease is increased by lifestyle factors such as a poor diet, smoking, alcohol and a lack of exercise. The risk can be reduced by healthy lifestyle choices: a balanced diet, not smoking, limiting alcohol and exercising regularly.
Risk factors do not act alone, and they often combine. For example, a poor diet high in fat together with a lack of exercise raises the risk of both coronary heart disease and Type 2 diabetes. Data on these diseases is often shown in tables or graphs, and you may be asked to describe a trend (for example that heart disease risk rises with the number of cigarettes smoked) and to suggest, but not prove, that one factor causes the disease. A correlation in the data is not always proof of cause, because other factors may also be involved.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style4 marksDescribe four different ways that pathogens can be spread from one person to another, giving an example of how each could be reduced.Show worked answer →
A 4-mark question on transmission and prevention.
Pathogens can be spread in water (reduced by treating drinking water), in food (reduced by safe food preparation and cooking), by air in droplets when people cough or sneeze (reduced by covering the mouth and isolating ill people), and by direct contact (reduced by good hygiene such as hand washing). Some are spread by vectors such as insects (reduced by controlling the vector).
Markers reward any four routes (water, food, air, direct contact, vectors) each with a sensible way to reduce it. Listing routes without a matching prevention loses the linked marks.
WJEC style3 marksExplain the difference between a communicable and a non-communicable disease, giving one example of each.Show worked answer →
A 3-mark explain question.
A communicable (infectious) disease is caused by a pathogen and can be passed from one organism to another, for example influenza caused by a virus. A non-communicable disease cannot be passed between people and is caused by other factors such as genetics or lifestyle, for example coronary heart disease, which is linked to diet, smoking and lack of exercise.
Markers reward: communicable spreads between people and is caused by a pathogen (with an example); non-communicable does not spread and has other causes (with an example). Calling cancer "infectious" is a common error.
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Sources & how we know this
- WJEC GCSE Biology specification (from 2016) — WJEC (2016)