Pathogens are microorganisms that cause infectious disease. Bacteria reproduce quickly and may release toxins; salmonella food poisoning is an example. Viruses are much smaller, live inside cells and make copies of themselves, bursting the cell; measles and HIV are viral. Fungi such as athlete's foot spread by spores. Protists cause malaria, carried by mosquitoes, which are vectors.
Diseases spread by direct contact, by water, through the air in droplets, or by vectors. Spread can be reduced by hygiene such as hand washing, isolating infected people, destroying vectors, and vaccination. Non-infectious diseases, such as most cancers and heart disease, cannot be passed on, but lifestyle risk factors like smoking and diet increase their likelihood.
Worked example
Why does handwashing reduce the spread of food poisoning?
- Bacteria like salmonella can be on hands.
- Washing with soap removes them.
Answer:Fewer bacteria reach food, so fewer people are infected.
Key words
- pathogen
- a microorganism that causes disease
- virus
- a tiny pathogen that reproduces inside cells
- vector
- an organism that carries a pathogen, e.g. a mosquito
- toxin
- a poison made by bacteria
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NGSS-referenced: HS-LS1-2