Waterborne outbreak management — DTM&H MCQ

Correct answer: D — Close the well and provide safe alternative water

The correct answer is D, close the well and provide safe alternative water. Once STEC O157:H7 is confirmed as the source linking multiple HUS cases to a common well, the outbreak control priority is immediate removal of the exposure source to prevent further infections while confirmatory environmental and epidemiological work continues. UKHSA outbreak management for STEC emphasises rapid identification and control of the vehicle of transmission, and a contaminated water supply used for drinking or irrigation is a recognised route requiring urgent exclusion and provision of an alternative safe supply. This action interrupts transmission at its source, protecting the wider population rather than relying on treating cases as they arise. Source control takes precedence over case management measures because STEC outbreaks linked to water or food vehicles can affect large numbers before individual cases present. Why the other options are wrong: A. Mass antibiotic treatment: Antibiotics are not recommended in STEC infection because they can increase Shiga toxin release and precipitate or worsen HUS, so mass treatment would be harmful rather than protective. C. Surveillance only: Passive surveillance does nothing to interrupt an identified ongoing exposure and would allow continued transmission from a known contaminated source. B. Vaccinate against STEC: No licensed human vaccine against STEC exists in the UK or elsewhere, making this option not clinically feasible. E. Treat well with molluscicide: Molluscicides target snails and other molluscs relevant to schistosomiasis or fascioliasis control, not bacterial contamination, and have no role in eradicating E. coli from water. Key point: When a point source (such as a well) is confirmed for a STEC outbreak, immediate exposure removal (closing the source and supplying safe water) takes priority over any individual case treatment, and antibiotics must specifically be avoided due to HUS risk.

Reference: UK Health Security Agency, Public health operational guidance for Shiga toxin-producing Escherichia coli (STEC), 2022; NHS inform, Escherichia coli (E. coli) O157: antibiotics not recommended due to risk of complications, https://www.nhsinform.scot/illnesses-and-conditions/infections-and-poisoning/escherichia-coli-e-coli-o157/