Health and disease
Health means being in a state of physical, mental and social well-being, not just free from disease. A disease is a condition that stops the body working properly. Pathogens are organisms that cause disease: bacteria, viruses, fungi and protozoa.
| Disease | Pathogen | How it spreads |
|---|---|---|
| Malaria | Plasmodium (protozoan) | bite of an infected female Anopheles mosquito |
| Cholera | bacterium | dirty water or food |
| Tuberculosis | bacterium | droplets in the air |
| Measles | virus | droplets in the air |
| Ringworm | fungus | touch |
Immunity and vaccination
Immunity is the body's ability to resist a particular disease. When a pathogen enters the body, white blood cells make antibodies that attack it, and some cells "remember" it. A vaccine contains a harmless form of a pathogen. It trains the body to make antibodies without making you ill, so the next real infection is fought off quickly.
Day 0 is the first vaccine dose. A booster dose is given on the day you choose. The second response is faster and higher than the first. (A simple model of antibody level, in arbitrary units.)
| Kind of immunity | How it is gained |
|---|---|
| Natural active | you catch the disease and your body makes antibodies |
| Artificial active | you are vaccinated |
| Natural passive | antibodies from the mother pass to the baby through the placenta and breast milk |
| Artificial passive | you are given ready-made antibodies by injection |
Key terms
- Pathogen
- An organism that causes disease.
- Antibody
- A protein made by white blood cells to fight a pathogen.
- Immunity
- The ability to resist a disease.
- Vaccine
- A harmless form of a pathogen used to give immunity.
Summary
- Disease is caused by pathogens and prevented by hygiene, clean water, vector control and vaccination.
- Antibodies fight pathogens and memory cells give faster protection next time.
- Immunity can be natural or artificial, active or passive.