Health, disease, immunity and hygiene
What this domain tests
Definitions of health and disease, pathogens and vectors, transmission routes, the body's three lines of defence, immunity and vaccination, and hygiene measures. Expect questions interpreting disease data and explaining why antibiotics fail against viruses.
Core rules
- Health is physical, mental and social wellbeing, not merely the absence of disease. Communicable diseases spread between people; non-communicable diseases such as cancer, diabetes and hypertension do not.
- Pathogens include bacteria (tuberculosis, cholera, typhoid), viruses (HIV, measles, influenza), protozoa (malaria, caused by Plasmodium) and fungi (athlete's foot). The malaria vector is the female Anopheles mosquito; the mosquito is not the pathogen.
- First-line defences: intact skin, mucus, cilia, stomach acid, tears and saliva. Second line: phagocytes engulf pathogens, with inflammation and fever. Third line: lymphocytes produce antibodies specific to antigens, and memory cells give long-lasting immunity.
- Active immunity follows infection or vaccination; the body makes its own antibodies, so it is slow to develop but long-lasting. Passive immunity, from maternal antibodies across the placenta or in colostrum, or from an antiserum, is immediate but short-lived.
- Antibiotics act on bacteria, not viruses, and overuse selects resistant strains.
- Hygiene: safe water, sewage disposal, hand-washing, food hygiene, vector control and isolation of cases.
Worked example
Explain why a child vaccinated against measles rarely catches it later. The vaccine contains weakened or inactive antigens. Lymphocytes recognise them as foreign, produce antibodies and leave memory cells behind. On later exposure, memory cells divide rapidly and produce antibodies within hours, destroying the virus before symptoms appear. This is active, artificially acquired immunity, because the child's own body made the antibodies.
Traps that cost marks
Saying antibiotics cure influenza. Calling a virus a cell. Claiming passive immunity lasts a lifetime. Naming the mosquito as the cause of malaria. Confusing antigen with antibody.