Acute watery diarrhoea in a cholera outbreak
Cholera kills by dehydration, sometimes within hours, and almost all deaths can be prevented with oral rehydration salts given early and in enough volume. The skills are simple: assess dehydration, give the right amount of fluid by weight, reassess often, and stop the spread.
- Setting: Oral rehydration point in a displacement camp; cholera outbreak declared 10 days ago; a cholera treatment unit 20 minutes away
- For clinical officers, nurses and community health workers at oral rehydration points and cholera treatment units
- Reviewed October 2026
The presentation
Hassan, 32, has had watery diarrhoea since last night: more than 10 times, large volumes, pale like rice water. He has vomited 3 times. He walked to the oral rehydration point with his brother. His tent neighbour was admitted to the cholera treatment unit two days ago.
| Sign | Value |
|---|---|
| Pulse | 108 per minute, radial pulse easy to feel |
| Blood pressure | 104/68 mmHg |
| Breathing rate | 20 per minute |
| Temperature | 36.8 °C |
| Weight | 52 kg |
| Conscious level (AVPU) | Alert, restless |
Tests at hand: Malaria rapid diagnostic test (RDT) · Blood glucose (finger-prick)
- Cholera Must not missStill possible
- Other acute watery diarrhoea (viral, bacterial)Still possible
- Bloody diarrhoea (dysentery, shigellosis)Still possible
- Malaria with diarrhoea Must not missStill possible
- Sepsis with diarrhoea Must not missStill possible
- Surgical abdomen presenting with diarrhoeaLess likely
Work through it
Read each question and decide your own answer first. Then open the model answer and see how the differential changes.
- Step 1 of 7 · Look
How dehydrated is Hassan? Use the four signs of the WHO assessment.
Model answer
Two or more signs in a column decide the class. Adapted from WHO, The treatment of diarrhoea (2005), Table 1. Sign No dehydration Some dehydration Severe dehydration Condition Well, alert Restless, irritable Lethargic or unconscious Eyes Normal Sunken Sunken Thirst Drinks normally Thirsty, drinks eagerly Drinks poorly or not able to drink Skin pinch Goes back quickly Goes back slowly Goes back very slowly Hassan is restless, his eyes are sunken, he drinks the cup of ORS you offer eagerly, and the skin pinch goes back slowly. He has some dehydration. He is not lethargic, can drink, and his radial pulse is easy to feel, so he is not in hypovolaemic shock.
Severe dehydrationA lethargic patient who cannot drink, with a weak or absent radial pulse, has severe dehydration: start IV Ringer's lactate at once.Differential now- Cholera Must not missLeading (moved up)
- Other acute watery diarrhoea (viral, bacterial)Still possible
- Bloody diarrhoea (dysentery, shigellosis)Still possible
- Malaria with diarrhoea Must not missStill possible
- Sepsis with diarrhoea Must not missLess likely (moved down)
- Surgical abdomen presenting with diarrhoeaLess likely
- Step 2 of 7 · Ask
What do you ask, and why does each question matter?
Model answer
- Blood in the stool: dysentery needs different treatment.
- Fever: in a malaria area, test for malaria; fever is not typical of cholera.
- Severe abdominal pain, distension, no wind (a surgical cause).
- How much and how recently he passed urine (a guide to dehydration and kidney function).
- Other illnesses: diabetes, heart or kidney disease (fluids need more care), HIV, malnutrition.
- Where the family gets drinking water, and whether others in the tent are ill (to target water, sanitation and hygiene).
No blood in the stool. No fever. Some cramping but no severe pain. He last passed a small amount of urine 8 hours ago. No known illnesses. The family collects water from a tap stand and stores it in an open bucket. His wife has had loose stools since this morning.
Differential now- Cholera Must not missLeading
- Other acute watery diarrhoea (viral, bacterial)Still possible
- Malaria with diarrhoea Must not missLess likely (moved down)
- Sepsis with diarrhoea Must not missLess likely
- Bloody diarrhoea (dysentery, shigellosis)Set aside for now (moved down)
- Surgical abdomen presenting with diarrhoeaSet aside for now (moved down)
- Step 3 of 7 · Test
You have a malaria RDT and glucose. Do you need them before treating?
Model answer
No test should delay rehydration. Suspected cholera in an outbreak is a clinical diagnosis: any person over 2 years with acute watery diarrhoea where cholera is known to be occurring.
- Malaria RDT: use it if there is fever in a malaria area. Hassan has no fever, so it is not needed today.
- Glucose: check it if a patient is lethargic, confused or has fitted, or is severely malnourished. Hassan is alert.
- Stool samples for laboratory confirmation are taken from some patients by the outbreak team, following the national surveillance plan; they do not change his treatment.
- Step 4 of 7 · Do
How much ORS does Hassan need in the next 4 hours, and how do you give it?
Model answer
WHO Treatment Plan B for some dehydration: about 75 mL of ORS per kg in the first 4 hours. For Hassan, 52 kg × 75 mL is about 3.9 litres (the WHO table gives 2.2 to 4 litres for anyone of 30 kg or more). If he wants more, give more.
- Frequent sips from a cup. Adults with dehydration can drink up to 750 mL an hour if needed.
- If he vomits, wait 5 to 10 minutes, then start again more slowly.
- Rice-based ORS, where available, is better than standard ORS for adults with cholera.
- Count and record the cups, and record each stool and vomit on his chart.
- Offer plain water as well during the maintenance phase.
When oral is not enoughSwitch to IV Ringer's lactate if signs of severe dehydration develop, if he becomes too tired to drink, vomits frequently, or the abdomen becomes distended.Differential now- Cholera Must not missLeading
- Other acute watery diarrhoea (viral, bacterial)Less likely (moved down)
- Malaria with diarrhoea Must not missLess likely
- Sepsis with diarrhoea Must not missLess likely
- Bloody diarrhoea (dysentery, shigellosis)Set aside for now
- Surgical abdomen presenting with diarrhoeaSet aside for now
- Step 5 of 7 · Do
Four hours later he is alert, not thirsty, eyes less sunken, skin pinch normal, and he has passed urine. He is still passing watery stools. What now? Does he need an antibiotic?
Model answer
He now has no signs of dehydration: move to Plan A. Continue ORS to replace ongoing losses, and keep reassessing every 1 to 2 hours while diarrhoea is profuse. Patients with cholera can need very large volumes in the first 24 hours.
WHO advises keeping suspected cholera patients under observation until the diarrhoea stops or becomes infrequent and small: he stays at the oral rehydration point, or is moved to the cholera treatment unit if it cannot observe him overnight.
Antibiotics: WHO recommends an effective oral antibiotic for suspected cholera with severe dehydration (for adults, doxycycline 300 mg as a single dose, chosen by local sensitivity), given once vomiting stops. For some dehydration, follow your national cholera protocol, which may extend antibiotics to patients with high stool output.
Plan C for adultsIf he deteriorates: severe dehydration needs IV Ringer's lactate 100 mL/kg: 30 mL/kg in the first 30 minutes, then 70 mL/kg over the next 2.5 hours, reassessing every 1 to 2 hours. - Step 6 of 7 · Do
What do you do to protect staff, his family and the camp?
Model answer
- Gloves and apron when handling stool and vomit; hand washing with soap or alcohol rub after every patient contact.
- Safe disposal of stool and vomit, and cleaning of the area, following the unit's infection prevention routine.
- Record him on the outbreak line list and report as the surveillance plan requires.
- Visit or message the household: his wife has early diarrhoea and needs ORS now. Give ORS packets and teach the family to prepare them.
- Treat drinking water at home and store it in a covered container with a tap or narrow neck; wash hands after the toilet and before food.
- Tell the water and sanitation team about the open storage bucket.
- Step 7 of 7 · Ask
What do you tell Hassan when he leaves, and what should bring him back?
Model answer
- Keep drinking ORS after each loose stool, and eat as soon as he feels like it.
- Come back at once if the stools become frequent again, he cannot drink, vomits everything, becomes very weak or sleepy, or passes little urine.
- Bring anyone at home with watery diarrhoea straight away; do not wait.
This is cholera. The danger is losing water, not the germ itself. Drink this ORS after every loose stool and come back straight away if you cannot drink or feel very weak. Bring your wife now so she can start ORS too.
Must-not-miss conditions
| Condition | Clues | What to do at first-level care |
|---|---|---|
| Severe dehydration and hypovolaemic shock | Lethargic or unconscious, sunken eyes, drinks poorly, skin pinch very slow; weak or absent radial pulse, low BP. | IV Ringer's lactate 100 mL/kg (30 mL/kg in 30 minutes, then 70 mL/kg in 2.5 hours); ORS as soon as he can drink; antibiotic once vomiting stops. |
| Cholera in vulnerable people | Pregnancy, older age, malnutrition, heart or kidney disease, young children. | Lower threshold for observation; give fluids with frequent reassessment for fluid overload; follow national protocol for antibiotic choice in pregnancy. |
| Malaria | Fever in a malaria area, with or without diarrhoea. | RDT; treat per protocol; pre-referral artesunate if severe. |
| Dysentery or sepsis | Blood in the stool; or fever, fast breathing, confusion, low BP out of proportion to the fluid loss. | Antibiotic per protocol; refer if severe or not improving. |
Decision at first-level care
Hassan has suspected cholera with some dehydration during a declared outbreak. He is rehydrated with about 3.9 litres of ORS over 4 hours (Plan B), reassessed, moved to Plan A once rehydrated, and kept under observation while the diarrhoea is profuse. His household is reached the same day, and the case is reported.
Source: WHO The treatment of diarrhoea: a manual for physicians and other senior health workers (2005); Sphere handbook (2018); WHO and ICRC Basic emergency care (2018).
- Some dehydration, able to drink: Plan B with ORS 75 mL/kg over 4 hours at the oral rehydration point or treatment unit.
- No dehydration: Plan A, ORS after each stool, home with return advice.
- Rehydrated but still passing large watery stools: keep under observation, reassess every 1 to 2 hours.
- Vulnerable patient (older, pregnant, malnourished, chronic illness) with mild diarrhoea: observe longer before discharge.
- Severe dehydration or shock: start IV fluids now and move to the cholera treatment centre or hospital.
- Unable to drink, repeated vomiting or abdominal distension on ORS.
- Confusion, fits, low glucose, or no urine after rehydration.
- Blood in the stool with high fever, or a suspected surgical cause.
Key learning points
- In an outbreak, suspect cholera in anyone over 2 years with acute watery diarrhoea; tests must not delay rehydration.
- Assess dehydration with four signs: condition, eyes, thirst and skin pinch.
- Some dehydration: ORS 75 mL/kg in 4 hours, then reassess. Severe: IV Ringer's lactate 100 mL/kg in 3 hours for adults.
- Antibiotics are for severe dehydration (doxycycline 300 mg once for adults), per national protocol for others.
- Every case is a household and a water source: reach the family the same day.
Sources
- World Health Organization. The treatment of diarrhoea: a manual for physicians and other senior health workers, 4th revision. 2005 (ISBN 9241593180). Table 1, dehydration assessment; Table 2, Plan B (75 mL/kg in 4 hours; 2200 to 4000 mL for 30 kg or more; adults up to 750 mL an hour); Table 3, Plan C (100 mL/kg Ringer's lactate, 30 mL/kg in 30 minutes then 70 mL/kg in 2.5 hours for older patients); section 5, when to suspect cholera, observation, rice-based ORS, IV if tired or vomiting; antibiotics for severe dehydration given when vomiting stops; Annex 7, doxycycline 300 mg once for adults.
- World Health Organization. IMAI district clinician manual: hospital care for adolescents and adults, volume 1. 2011. Section 3.1.2, hypovolaemic shock from cholera: most can be rehydrated with ORS; IV for those in shock or unable to drink.
- World Health Organization and International Committee of the Red Cross. Basic emergency care: approach to the acutely ill and injured. Participant workbook. 2018 (ISBN 9789241513081). Rice-water stool suggests cholera; gloves, aprons, isolation precautions and reporting to public health.
- Sphere Association. The Sphere handbook: humanitarian charter and minimum standards in humanitarian response, 4th edition. 2018. Water supply, sanitation and hygiene promotion; household water treatment and safe storage; outbreak preparedness and response.