12.1 Disease

2026 Syllabus Objectives

By the end of this topic, you should be able to:

1. Describe a pathogen as a disease-causing organism
2. Describe a transmissible disease as a disease in which the pathogen can be passed from one host to another
3. Understand that a pathogen may be transmitted through direct contact (including blood or other body fluids) and indirectly (including from contaminated surfaces or food, from animals, or from the air)
4. Describe the human body's barriers to the entry of pathogens — skin, hairs in the nose, mucus, stomach acid
5. Understand the role of the mosquito as a vector of disease
6. Describe the malarial pathogen as an example of a parasite and explain how it is transmitted
7. Describe the control of the mosquito that transmits malaria with reference to its life cycle
8. Explain that human immunodeficiency virus (HIV) is a viral pathogen
9. Describe how HIV is transmitted
10. Understand that HIV infection may lead to Acquired Immune Deficiency Syndrome (AIDS)
11. Describe the methods by which HIV may be controlled
12. Describe cholera as a disease caused by a bacterium, which is transmitted in contaminated water
13. Explain the importance of a clean water supply, hygienic food preparation, good personal hygiene, waste disposal and sewage treatment in controlling the spread of cholera
14. Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, resulting in diarrhoea, dehydration and loss of ions from the blood
15. Describe the effects of excessive consumption of alcohol — reduced self-control, depressant effect, effect on reaction times, damage to liver and social implications
16. Describe the effects of tobacco smoke and its major toxic components (nicotine, tar and carbon monoxide) — strong association with bronchitis, emphysema, lung cancer and heart disease; and the association between smoking during pregnancy and reduced birth weight of the baby

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