Wedding-feast outbreak of vomiting and diarrhoea in a village of 2,100
On a Monday morning the district surveillance officer receives reports of 43 people with diarrhoea and vomiting in a village of 2,100. All had attended a wedding feast on Saturday evening that was eaten by 180 guests. Symptoms began 6–18 hours after the meal. Nine people have been admitted with dehydration and a 70-year-old woman is in hypovolaemic shock. The menu included chicken biryani cooked that morning and held at room temperature until 8 pm, a milk-based dessert, and untreated well water served from a single tank. Two food handlers have paronychia. The district hospital can perform stool culture but results take 72 hours; no viral or toxin testing is available locally. The village council is demanding that the kitchen be closed permanently, and local journalists are asking for a comment.
1. Set out your priority actions for the first 24 hours and justify each one by what it prevents or rules out.
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Life-saving work comes first, then source control, then evidence gathering - in that order, and in parallel where possible.
- Treat the shocked woman and the dehydrated now. Oral rehydration solution for those who can drink, Ringer's lactate for the shocked patient. Rehydration must not wait for microbiology results.
- Build a line list and a case definition (acute watery diarrhoea or vomiting within 72 hours of the feast) so that the denominator and the case count are defensible.
- Collect specimens before antibiotics: stool and vomitus from cases, remnants of the biryani and dessert, the well water and tank water, and swabs from the food handlers' paronychia.
- Interpret the incubation period. Vomiting at 1–6 hours points to preformed toxin (Staphylococcus aureus, Bacillus cereus emetic type); 6–18 hours fits Clostridium perfringens or the diarrhoeal B. cereus type. The wide range and the room-temperature biryani make a preformed or sporulating toxin plausible, while the single well-water tank leaves cholera and other faecal-oral pathogens firmly on the list.
- Immediate environmental measures: chlorinate the tank, advise boiling or chlorinated water, stop use of the well pending testing, exclude symptomatic food handlers until 48 hours symptom-free, inspect the kitchen and hand-washing facilities.
- Notify the next level and document everything from the outset, because the council and press are already involved.
2. Calculate the attack rate and design the quickest study that could implicate a particular food or water source. What are the pitfalls here?
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Crude attack rate among guests = 43 ÷ 180 = 23.9%. That figure alone only shows a substantial risk among attendees; it cannot identify the vehicle.
Design: a retrospective cohort study of all 180 guests is the fastest credible design because the population is known and enumerated.
- Interview every guest with a standard questionnaire: which dishes were eaten and how much, which water source was drunk, time of onset, symptoms.
- Build 2 × 2 tables for each exposure (ate biryani, ate dessert, drank well water) and calculate food-specific attack rates and risk ratios, comparing attack rate in exposed versus unexposed.
- Also test whether symptomatic guests are over-represented compared with villagers who did not attend - a non-attendee rate near background argues for a point-source vehicle rather than person-to-person spread.
Pitfalls to anticipate:
- Everyone may have eaten the biryani, so that exposure has no unexposed comparison and cannot be analysed; the dessert and water may be the only discriminating variables.
- Recall bias after media coverage, and guests who cannot be traced.
- The well water could have been drunk by non-attendees too, which will dilute or clarify the association.
- Culture may be negative by the time samples are taken; a negative result does not exclude a toxin-mediated outbreak.
3. The village council wants the kitchen permanently closed and journalists want a quote. How do you handle this?
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Separate the public-health action from the punitive demand, and be explicit about uncertainty.
- Temporary closure pending inspection is proportionate and easily justified: it removes ongoing exposure while the kitchen's water supply, refrigeration, holding times and handler hygiene are checked. Permanent closure is not supported by the evidence at this stage and would be a decision for local government, not for the health team.
- State what is established and what is not. Established: a large point-source-type outbreak following a specific meal. Not established: the organism, the vehicle, or fault. Say so plainly, because premature attribution invites litigation and destroys cooperation.
- Focus the message on what people can do now: boil or chlorinate water, reheat food thoroughly, wash hands, and seek care early for bloody diarrhoea, confusion, or inability to drink.
- Protect individuals: do not name food handlers or patients; explain the 48-hour exclusion rule as a control measure, not as punishment.
- Plan the follow-up: report results when available, brief the council in writing, and agree a single spokesperson so the press receives consistent information.
A permanent closure announced before the water tank is even tested risks condemning the wrong source and missing the real one.