Health and diseaseSpec 4.2.2.5
In short
Health is the state of physical and mental well-being. Communicable diseases are caused by pathogens and can spread from person to person; non-communicable diseases cannot. Diseases can interact: immune system defects make infection more likely, viruses can trigger cancers, immune reactions can trigger allergies, and severe physical ill health can lead to depression.
Health is the state of physical and mental well-being.
Diseases, both communicable and non-communicable, are major causes of ill health. A communicable disease is caused by a pathogen and can spread from person to person. A non-communicable disease cannot. Other factors including diet, stress and life situations may have a profound effect on both physical and mental health.
How different types of disease interact
| Interaction | Meaning |
|---|---|
| Immune system defects | Defects in the immune system mean that an individual is more likely to suffer from infectious diseases |
| Viruses and cancer | Viruses living in cells can be the trigger for cancers |
| Immune reactions and allergies | Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma |
| Physical and mental health | Severe physical ill health can lead to depression and other mental illness |
If asked how two diseases interact, name both diseases and say how one makes the other more likely, for example ‘a weak immune system makes infection more likely’.
Written and checked against the AQA GCSE Biology (8461) specification · Updated October 2026