A COMMUNITY WATERBORNE OUTBREAK OF SALMONELLOSIS AND THE EFFECTIVENESS OF A BOIL WATER ORDER

Objectives. A 1993 large waterborne outbreak of Salmonella typhimurium infections in Gideon, Mo, a city of 1100 with an unchlorinated commun ity water supply, was investigated to determine the source of contamin ation and the effectiveness of an order to boil water. Methods. A surv ey of household members in Gideon and the surrounding township produce d information on diarrheal illness, water consumption, and compliance with the boil water order. Results. More than 650 persons were ill; 15 were hospitalized, and 7 died. Persons consuming city water were more likely to be ill (relative risk [RR] = 9.1, 95% confidence interval [ CI] = 2.9, 28.4), and the attack rate increased with increased water c onsumption. S. typhimurium was recovered from samples taken from a cit y fire hydrant and a water storage tower. Persons in 318 (30/98) of ci ty households had drunk unboiled water after being informed about the boil water order, including 14 individuals who subsequently became ill . Reasons for noncompliance included ''not remembering'' (44%) and ''d isbelieving'' (25%) the order. Conclusions. Communities with deteriora ting water systems risk widespread illness unless water supplies are p roperly operated and maintained. Effective education to improve compli ance during boil water orders is needed.