# Influenza is a communicable disease caused by a virus. Explain how the human body's defence mechanisms attempt to prevent the influenza virus from entering the body and, if it does enter, how the immune system responds to destroy it.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.2 Pathogens and infection · Explain · 5 marks

> Influenza ('flu') spreads between people via droplets released when an infected person coughs or sneezes. Each year, thousands of people in the UK are hospitalised as a result of influenza infections.

## Mark scheme (5 marks)

1. The mucus lining of the nose/trachea/airways traps pathogens (including viruses) before they can enter the body
2. Cilia waft/move the mucus (and trapped pathogens) away from the lungs towards the throat so pathogens are removed
3. If the virus enters the body, white blood cells / phagocytes can engulf and destroy the pathogen by phagocytosis
4. B-lymphocytes recognise the specific antigen on the influenza virus and produce complementary antibodies
5. Antibodies bind to the antigens on the influenza virus, neutralising/marking the virus for destruction / triggering an immune response that destroys the pathogen

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/influenza-is-a-communicable-disease-caused-fb05be5f) · Published by Druglandscape Ltd.