GCSE Biology · Edexcel 1BI0 · Topic 5A
Communicable diseases
Key points
- Health is complete physical, mental and social well-being. One disease can make a person more likely to get others, e.g. HIV weakens the immune system.
- Pathogens: bacteria, viruses, fungi and protists. Examples: cholera (bacterium, spread in dirty water, causes diarrhoea), tuberculosis (bacterium, airborne, lung damage), malaria (protist, spread by mosquitoes), chalara ash dieback (fungus).
- Ebola (virus, spread in body fluids) and Helicobacter (bacterium causing stomach ulcers) are also on the spec.
- STIs: chlamydia (bacterium) and HIV (virus) are spread by sexual contact; reduced by condoms, screening and treatment.
- Reduce spread with hygiene, clean water, isolating patients, killing vectors and vaccination.
- The lytic cycle: a virus injects its genetic material, the cell makes new viruses, then bursts. In the lysogenic cycle the viral DNA joins the host DNA and stays dormant for a time.
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A communicable disease is one caused by a pathogen that can be passed from one organism to another. This sub-topic covers the types of pathogen, the named diseases on the specification and the practical ways we stop them spreading.
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