Explain how a pathogen can spread from one person to another through contaminated water.

WJEC GCSE Biology (Wales) — 2.6.1 Pathogens and disease · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Cholera is a disease caused by a bacterium that can affect thousands of people in areas where clean water is not available.

Model answer (4 marks)

1. The bacterium contaminates the water supply, for example by sewage or animal waste entering a source.
2. A person drinks or uses the contaminated water.
3. The bacterium enters the body, usually through the mouth and stomach, and survives the acidic environment.
4. Inside the host it multiplies, producing toxins that damage the intestinal lining, leading to diarrhoea and dehydration.

Examiner tips

Use the word "contaminates" or "contamination" for step 1. Mention "drinks" or "uses" water for step 2. Explain that the pathogen survives the stomach and reaches the gut for step 3. Show that multiplication and toxin production cause disease for step 4.

Common mistakes

Mixing up the order of steps. Failing to mention the pathogen’s survival in the stomach. Using vague terms like "gets in" instead of "enters the body".

Mark scheme (4 marks)

Pathogen enters the water supply / water becomes contaminated with the pathogen (bacterium)
The contaminated water is consumed / drunk by a person
The pathogen enters the body and infects the host
The pathogen can reproduce / multiply inside the host, causing disease

Key terms in this question

pathogen · contaminated