CB5.1 — Health and disease (Edexcel 1SC0)
Types of disease
Communicable (infectious): caused by pathogens; can be passed between organisms. Non-communicable: not caused by pathogens; cannot spread between people (e.g. cancer, heart disease, diabetes).
Pathogens
| Pathogen | Size | Example | Treatment |
|---|---|---|---|
| Virus | 20–300 nm | HIV, influenza | Antiviral drugs; vaccines |
| Bacteria | 1–10 µm | TB, cholera | Antibiotics |
| Fungi | Varies | Athlete's foot, chalara ash dieback | Antifungals |
| Protist | 10–100 µm | Malaria (Plasmodium) | Antimalarials |
Transmission
- Direct contact: touching, sexual contact (e.g. HIV).
- Air droplets: sneezing, coughing (e.g. influenza, TB).
- Water: contaminated water (e.g. cholera).
- Vector: e.g. mosquito spreads malaria (Anopheles mosquito).
- Food: contaminated food (e.g. Salmonella).
Key diseases
HIV: virus; attacks helper T cells of immune system; leads to AIDS (immune system fails). Transmitted through blood and sexual contact.
TB (tuberculosis): bacteria (Mycobacterium tuberculosis); spread by air droplets; treated with antibiotics for 6+ months.
Cholera: bacteria (Vibrio cholerae); spread through contaminated water; produces severe diarrhoea; treated with rehydration and antibiotics.
Malaria: protist (Plasmodium); spread by Anopheles mosquito bite; kills millions annually; treated with antimalarial drugs.
Chalara ash dieback: fungus (Hymenoscyphus fraxineus); kills ash trees; spreads by wind-borne spores.
AI-generated · claude-opus-4-7 · v3-edexcel-combined-science