What is What is Germ Theory??

Germ Theory — GCSE History Revision

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The basics

Setting the Scene

📖 Setting the Scene

For centuries, doctors believed disease was caused by "bad air" (miasma) or imbalanced humours. Then in 1861, French scientist Louis Pasteur proved something revolutionary: microorganisms — invisible tiny living things — caused decay. And if germs caused decay, could they cause disease? By 1878, German doctor Robert Koch had proved exactly that, identifying specific germs for specific diseases. The 2,000-year-old miasma theory was dead. Medicine would never be the same.

▶ Pasteur & Germ Theory - BBC Teach (5 mins) ▶ Robert Koch - Simple History (6 mins)

What is Germ Theory?: The theory that specific microorganisms (germs/bacteria) cause specific diseases — published by Pasteur in 1861

Key terms

History glossary

What is Germ Theory?: The theory that specific microorganisms (germs/bacteria) cause specific diseases — published by Pasteur in 1861

Spotlight

Pasteur's Germ Theory (1861)

Key point: Pasteur proved germs existed and caused decay. He suggested they might cause disease — but didn't prove it himself.

Exam tip

Earn the mark scheme marks

📝 Exam Technique: Germ Theory as a Turning Point

This is THE biggest turning point in medicine:

Before Germ Theory: Couldn't prevent, couldn't cure (didn't know cause)

After Germ Theory: Could prevent (vaccines, hygiene), could eventually cure (antibiotics)

BUT: Change was SLOW. Many doctors resisted. Public health reforms took decades.

Link to other factors: Technology (microscopes), individuals (Pasteur, Koch), war (rivalry), government (funding)

🏫 Edexcel 1HI0/10 — Medicine in Britain (Paper 1, Option 1HI0/10): This topic is tested on Paper 1 alongside the Historic Environment (Western Front). Edexcel question types differ from AQA:

"Describe two features of..." (4 marks) — Identify a feature (1 mark) + supporting detail (1 mark). Write two separate PEEL-style paragraphs. No evaluation needed.
"Explain why..." (12 marks) — Explain two or three reasons with specific evidence. Level 3 (7–9 marks) requires explained reasons; Level 4 (10–12 marks) requires explanation showing how factors connect or reinforce each other.
"How far do you agree that..." (16 marks + 4 SPaG) — Extended writing. Two sides: evidence FOR the statement, evidence AGAINST. Reach a supported judgement. Level 4 (13–16 marks) requires a consistently argued judgement. SPaG marks reward accurate spelling of key historical terms.

Now try it yourself

Quiz · Question 1 of 8

In which year did Louis Pasteur publish his Germ Theory?

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