Health, Disease and the Immune System — AQA GCSE Biology

This topic covers what health means, the different types of disease and how they can interact.

What is health?

Health is a state of physical and mental wellbeing, not merely the absence of disease. Diseases — both communicable and non-communicable — are a major cause of ill health. Other factors affecting health include diet, stress and life situations.

Communicable and non-communicable diseases

• Communicable diseases are caused by pathogens and can be spread between organisms (e.g. measles, influenza).
• Non-communicable diseases cannot be spread and tend to last a long time (e.g. coronary heart disease, many cancers, diabetes).

How diseases interact

Different types of disease can interact:

• A weakened immune system makes a person more likely to suffer from communicable diseases.
• Some viruses living in cells can be the trigger for cancers (e.g. HPV and cervical cancer).
• Immune reactions caused by a pathogen can trigger allergies such as skin rashes and asthma.
• Severe physical ill health can lead to mental illness such as depression.

Exam tips

• Define health as physical and mental wellbeing.
• Distinguish communicable (spread by pathogens) from non-communicable (cannot be spread) diseases with examples.
• Be ready to explain interactions between diseases (e.g. weak immune system → more infections; viruses → cancer).