Describe cholera and its contaminated-water route
Identify a bacterial cause and trace an indirect route to a new host.
Section 10.1 · Diseases and immunity
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall indirect water transmission and disease-control measures.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which group contains the cholera pathogen?
What you will learn
- Agent and vehicle are different
- Link route control with the known agent
WHO background: cholera cause and transmission. Original classroom questions; this model does not diagnose infection.
Agent and vehicle are different
Cholera is a disease caused by the bacterium Vibrio cholerae. Contaminated water can transmit the bacterium to another host when consumed. The water is the vehicle and the bacterium is the pathogen; neither a symptom such as diarrhoea nor the water itself is the causal organism.
In the required route, pathogen-containing faeces can contaminate a water source, then drinking that water brings bacteria into the digestive system. Contaminated food can also be a route, but the syllabus specifically requires the contaminated-water explanation. A clear-looking water sample does not establish absence of this bacterium.
Link route control with the known agent
A clean water supply and appropriate sewage treatment can reduce this faecal-contamination route. Explain where each measure interrupts the chain rather than claiming that water treatment makes the recipient produce antibodies or that every diarrhoeal illness must be cholera. The name of a symptom does not identify a particular pathogen.
This classroom sequence uses established biological mechanisms, with cholera’s toxin and osmotic effects taught next. It does not identify real infections from symptoms. The WHO source linked in the course materials supports the bacterial and contaminated-water description; original practice scenarios are invented and do not represent actual outbreak case records.
Pause and explain
Which chain explains the required cholera route?
Worked example
A supplied cholera route uses pathogen-containing water. Identify the causal agent and transmission vehicle.
Show the worked solution
- The agent is a bacterium.
- The vehicle is contaminated water.
Answer Agent: Vibrio cholerae bacterium. Vehicle: contaminated water.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name the causal organism group and required transmission vehicle for cholera.
Give me a hint
Keep agent and vehicle separate.
Compare my reasoning
- Vibrio cholerae is a bacterium.
- It can reach a host in consumed contaminated water.
Bacterium; contaminated water.
Look for these in your work
- Name the group
- Name the vehicle
Explain a sewage-to-host chain for the supplied cholera model.
Give me a hint
Trace contamination and ingestion.
Compare my reasoning
- Sewage contains pathogen-bearing faecal material.
- Water becomes contaminated and is swallowed by another host.
Pathogen-containing sewage → contaminated water → ingestion of the cholera bacterium by another host.
Look for these in your work
- Include faecal contamination
- Include consumption
An invented case lists diarrhoea but gives no identified organism or water-exposure evidence. Does it establish cholera?
Give me a hint
A symptom can have different causes.
Compare my reasoning
- Diarrhoea is not specific proof of this bacterium.
- The agent and route are not established.
No; the symptom alone does not establish cholera or its transmission route.
Look for these in your work
- Avoid diagnosing from one symptom
- Name missing evidence
Common mistakes
- Calling diarrhoea the pathogen.
- Inferring cholera from symptoms alone.
What can you explain now?
Which chain explains the required cholera route?
Compare with the explanation
Contaminated water is swallowed and carries the bacterium into a host
This is an indirect water route.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Trace the cholera route and mark two controls without calling water the pathogen.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.