Twenty-Seven Cases of Watery Diarrhoea in Eleven Days

Attack rate. The population at risk is the cluster around the pump: 60 households × about 5 persons = approximately 300 people. Attack rate = 27 ÷ 300 = 0.09 = 9% over 11 days.

Case fatality ratio. 2 deaths ÷ 27 cases = 7.4%.

Is it an outbreak? Yes. An outbreak is the occurrence of more cases of a disease than expected in a defined area over a defined period. Three findings together settle it:

1. Time and place clustering - nearly all cases within 200 m of one pump, in 11 days, with a cracked apron next to an open drain.
2. A rate far above baseline - a sub-centre would normally see a handful of sporadic diarrhoea cases a month, not 9% of a defined neighbourhood in under two weeks.
3. Two deaths in children under five - a 7.4% case fatality ratio is far too high for diarrhoea managed with ORS and points to a virulent pathogen, most plausibly cholera, and to delayed care.

Why both figures matter: the attack rate shows how widely the exposure has spread and whether it is still growing; the case fatality ratio shows how severe and how badly managed the cases are. A high attack rate with low mortality is a water problem; a low attack rate with high mortality is a treatment-access problem. Here both are abnormal, so the response must address water and case management at once.

Practical caveat: 27 is the number who presented. Active house-to-house search will almost certainly raise it, so treat 9% as a floor, not a final estimate.

Correct chain and sequence:

1. ANM → Medical Officer of the PHC/sub-centre, immediately on seeing a cluster (not a single case) - a phone call the same day, followed by the line list.
2. Medical Officer → District Surveillance Officer, verbally within 24 hours, with a written or portal line list covering age, sex, village, date of onset, water source, treatment and outcome.
3. DSO records it on the Integrated Health Information Platform, the national reporting layer of the Integrated Disease Surveillance Programme, and grades the event.
4. DSO activates the Rapid Response Team, which should reach the village within 24–48 hours to do the epidemiological investigation, collect stool/rectal swabs in Cary-Blair transport medium and water samples, and start control measures.
5. Cholera, if confirmed, is notified under the state public health law to the municipal or district health authority, because it triggers statutory water and sanitation action, not just clinical care.

What the silence breached: diarrhoea deaths and a case cluster are reporting priorities under the Integrated Disease Surveillance Programme, and the ANM was the first point of detection. The register entry satisfies record-keeping; it does not satisfy surveillance, because surveillance exists to move information upward fast enough to permit intervention. An 11-day delay cost the system the chance to chlorinate the source before most of the 27 cases occurred, and it put the two deaths squarely inside the window when they might have been prevented.

Judgement point: the failure is not that the ANM wrote nothing down. It is that she did not escalate. A well-kept register that nobody reads is not surveillance.

Recommendation: stop the pump immediately, but only together with a replacement supply. Shutting a source without an alternative pushes the same 300 people onto a worse source - the open drain or a contaminated well - and can widen the outbreak. In practice: seal or cordon the pump the same day, tanker in chlorinated water or reconnect the piped supply, and keep the pump closed until the apron is repaired, the drain diverted, and the water tests clear on two consecutive samples.

Immediate control measures:

• Water: H2S vial test on the pump and on neighbouring sources; sanitary survey of the 60 households; superchlorination of wells and storage; residual free chlorine of about 0.5 mg/L at the point of use.
• Case finding and treatment: house-to-house search for cases, and free ORS at every household.
• Case management protocol to issue that day: Plan A (no dehydration) - extra fluids and ORS at home after each loose stool, about 50–100 mL for under-2s and 100–200 mL for older children. Plan B (some dehydration) - ORS 75 mL/kg over 4 hours under observation. Plan C (severe dehydration) - intravenous Ringer's lactate, then ORS as soon as the patient can drink.
• Zinc for every child under five: 10 mg daily under 6 months, 20 mg daily for 6 months to 5 years, for 14 days - it shortens the episode and reduces recurrence.
• Antibiotics: not for watery diarrhoea without blood; they are indicated only for suspected cholera with severe dehydration, and then on the protocol advised by the DSO, not routinely.
• Continue feeding and breastfeeding; do not withhold food.

Judgement point: the pump is a symptom. The decision has to be paired with a safe substitute, or the intervention will make the outbreak worse than the pump did.