# Explain why communicable diseases can spread rapidly through a population.

> AQA GCSE Biology (8461) — 4.3.1 Communicable diseases · Explain · 4 marks

## Mark scheme (4 marks)

1. Communicable diseases are caused by pathogens (e.g. bacteria, viruses, fungi, protists)
2. Pathogens can be transferred from one infected person to another (person-to-person transmission)
3. Pathogens can be spread by multiple routes, e.g. direct contact, contaminated water/food, air/droplets, vectors
4. Once inside a new host, pathogens can reproduce rapidly, increasing the number of infected individuals

## Key terms

- [communicable disease](https://www.gradenine.co.uk/glossary/communicable-disease)

## Related

- [Revision notes for AQA GCSE Biology (8461)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-communicable-diseases-can-spread-5759e50d) · Published by Druglandscape Ltd.