A community outbreak of Campylobacter jejuni infection from a chlorinated public water supply

An outbreak of Campylobacter jejuni infection occurred in a South Wales Valleys housing estate. Illness in estate residents was associated with tap water consumption [population attributable risk (PAR) 50%, relative risk (RR) 2.53, 95% confidence interval (CI) 1.9-3.37] and residence in the upper estate (PAR 49%, RR 2.44, 95% CI 1.83-3.24). Amongst upper estate residents, rates of diarrhoeal illness increased with rates of water consumption (OR 18, 95% CI 3.5-92.4 for heaviest consumers, chi2 trend P<0.0001). The upper estate received mains water via a covered holding reservoir. A crack in the wall of the holding reservoir was identified. Contamination with surface water from nearby pasture land was the likely cause of this outbreak. Service reservoirs are common in rural communities and need regular maintenance and inspection. The role of water in sporadic cases of campylobacter enteritis may be underestimated.