Cholera: Waterborne Transmission and Oral Rehydration
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Cholera is caused by the bacterium Vibrio cholerae, transmitted through water contaminated with faeces from infected people. It causes severe diarrhoea leading to dehydration. Treatment involves oral rehydration therapy (ORT): a solution of salts and sugars in clean water. Prevention requires improved sanitation and clean water supply.
Cholera is a named disease in the Cambridge 0610 syllabus and appears regularly in exam questions. The link between poor sanitation, water contamination and disease spread is a common 4-mark question.
How cholera spreads
The cholera bacterium (Vibrio cholerae) lives in the intestines of infected people. It is released in faeces. If sewage contaminates drinking water: for example, when sanitation infrastructure is inadequate or damaged by flooding: the bacteria enter the water supply.
People become infected by drinking contaminated water or eating food washed in it. The bacteria colonise the small intestine and produce a toxin that causes the intestinal lining to secrete large amounts of water and salts into the gut lumen, leading to profuse watery diarrhoea.
Symptoms and treatment
The main symptom is severe watery diarrhoea, which can lead to rapid and dangerous dehydration and loss of mineral ions. Without treatment, the fluid and electrolyte loss can cause circulatory shock and death within hours.
Oral rehydration therapy (ORT) is the primary treatment. ORT is a carefully balanced solution of salts and glucose dissolved in clean water. The glucose enables sodium ions to be co-transported across the intestinal lining, and water follows by osmosis. This replaces lost fluid and ions even while the diarrhoea continues. Antibiotics may also be used but ORT is the life-saving intervention.
Prevention
Cholera prevention focuses on breaking the faecal-oral transmission route: proper sewage treatment to prevent faecal contamination of water; clean drinking water through water treatment plants, chlorination or boiling; good personal hygiene including handwashing with soap; and safe food handling practices.
Cholera outbreaks are most common in areas with poor sanitation infrastructure, often following natural disasters that damage water and sewage systems. Vaccination provides short-term protection and can be used in outbreak situations.
Try a focused question (3 marks)
Suggest why cholera spreads more rapidly in areas with poor sanitation after flooding.
Show the answer and marking guidance
Flooding mixes sewage containing cholera bacteria with drinking water supplies.
People drink the contaminated water because clean water is unavailable.
More people become infected and excrete bacteria, further contaminating the water supply.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Saying cholera is caused by dirty water rather than by bacteria in contaminated water.
Confusing oral rehydration therapy with antibiotics: ORT replaces fluid and salts, it does not kill bacteria.
Describing cholera as an airborne disease: it is waterborne (faecal-oral route).
Not explaining why glucose is included in ORT: it enables sodium and water absorption.