Twenty-two cases of diarrhoea in Chak 96
In Chak 96, 22 of 180 residents, including 9 children under five, report watery diarrhoea within 72 hours. Nearly all of them draw water from a hand pump in a courtyard three metres from a soakage pit that was desilted last week. A second hand pump 15 metres away serves the mosque; its users include only 2 of the 22 cases. A field kit shows turbidity of 25 NTU and a positive thermotolerant coliform (E. coli) result. The naib-tehsildar has Rs 25,000 from the tehsil sanitation head and 48 hours before the assistant commissioner's review. The options on the table are: (i) chlorinate the affected pump with bleaching powder; (ii) distribute ORS and zinc sachets; (iii) sink a new hand pump 25 m from the pit; (iv) hold a health-education session; (v) close the pump. The union council chairman argues that chlorination alone is enough and wants the pump reopened at once because 'the water looks clear in a glass'.
1. What does the pattern of cases, the distance to the soakage pit and the field-kit results establish about the source of the outbreak? Why does turbidity of 25 NTU matter for chlorination?
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What the pattern shows.
- One pump, used by almost all cases, three metres from a soakage pit desilted a week ago: a short, direct pathway for faecal material into a shallow, unsealed intake. Desilting disturbs the pit and pushes liquid into the surrounding soil.
- The second pump fifteen metres away, with only 2 cases, acts as a natural control: the exposure is local, not village-wide. This is a point-source outbreak, not a food-borne or seasonal one.
- A positive thermotolerant coliform/E. coli result is the specific indicator of faecal contamination; it is not a general 'dirt' reading.
Why turbidity matters. Chlorine is consumed by organic and particulate matter before it reaches micro-organisms, and particles can shield bacteria inside flocs. Above roughly 5 NTU, chlorination becomes unreliable; at 25 NTU a standard dose may leave a free residual near zero and still leave viable organisms. So chlorination must follow, not replace, turbidity reduction (settling, filtration, or an alternative source), and the water must be retested before the pump is reopened. In the interval, boiling for one minute or water from the mosque pump is the only dependable advice.
The epidemiological reasoning and the chemistry point to the same order of operations: fix the pathway, reduce the turbidity, then disinfect, then verify.
2. Allocate the Rs 25,000 across the five options for the 48-hour window, with costs, and justify the sequence. Why are ORS and zinc in the package when they do not cure the infection?
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Package within Rs 25,000:
- Close the pump and announce a safe point (mosque pump/tankered water): nil - protects the remaining 158 residents immediately.
- ORS: two sachets per person for 180 people = 360 × Rs 12 = Rs 4,320.
- Zinc for the 9 under-fives: 20 mg daily for 14 days = 18 strips at Rs 60 = Rs 1,080.
- Seal/relocate the soakage pit, apron and drainage around the pump: Rs 8,000.
- Bleaching powder, 5 kg: Rs 1,500; education material and one session: Rs 1,000.
- Committed: Rs 15,900. Balance: Rs 9,100 for a repeat bacteriological/H2S test and contingency.
Sequence: hour 0–4, close and warn; hour 0–24, ORS/zinc plus referral of any child with sunken eyes, lethargy or no urine; day 2–4, fix the source, then shock-chlorinate after turbidity is reduced, and retest before reopening.
Why the new hand pump is not in this week's money: at 25 m it is the right durable answer, but it cannot be sited, sanctioned and commissioned inside the review window; it belongs in the next ADP request, not this budget.
Why ORS and zinc despite no cure: ORS does not treat the infection - it replaces water and electrolytes and prevents the deaths that come from dehydration. Zinc shortens the episode and reduces recurrence. Antibiotics are not indicated for most acute watery diarrhoea and would consume the budget for no benefit.
3. The chairman says the water 'looks clear' and should be reopened. Answer him, and draft the one message you would give the community.
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'The water looks clear' is not a test. Pathogens are invisible at any turbidity. A glass of water can be perfectly clear and still carry an infective dose of E. coli or rotavirus; clarity speaks only to suspended solids, not to microbiology. Reopening on that basis would restart an outbreak that already has 22 cases and 9 children under five in it, and the file would record that the department was warned and proceeded anyway.
What to tell him, on paper: chlorination at 25 NTU will not hold a safe residual; the pump stays closed until a repeat test is negative; the pit is being sealed this week; and his help is wanted in monitoring the sealed pit and reporting seepage. Giving him a defined role converts the argument into a joint duty.
Community message (one paragraph, read out at the mosque and the school): 'This pump is closed until the laboratory says the water is safe. Until then, use the mosque pump, or boil water for one minute and let it cool. Wash hands with soap after using the toilet and before feeding a child. Any child with loose stools should get ORS and zinc, and should go to the BHU at once if there is no urine, sunken eyes or drowsiness. The pit beside the pump is being sealed this week; please report any seepage to the patwari.'
Note what the message does and does not do: it gives a date-free but concrete action set, names the referral sign, and makes no promise the laboratory has not yet made.