In November 2007, 450 m(3) of treated wastewater leaked into the drinking water distribution system contaminating the drinking water of over 10,000 inhabitants of Nokia, Southern Finland. Nearly 1,000 people visited the health centre because of gastroenteritis during the following 5 weeks. A wide range of enteric pathogens was found in the patients. The authors used the 16-plex PCR to investigate whether the five major diarrheagenic Escherichia coli pathotypes (EPEC, ETEC, STEC, EIEC or EAEC) were present in the contaminated drinking water and in the patients' stool samples. The contaminated drinking water was positive for genes characteristic of various E. coli pathotypes: pic, invE, hlyA, ent, escV, eae, aggR, stx(2) , estIa and astA. These genes, except stx(2), hlyA and invE, were also detected in the stool samples of the patients linked to this outbreak. A sorbitol positive, streptomycin resistant STEC strain was isolated from the drinking water, and belonged to the serotype O100:H(-), produced Stx2 toxin (titre 1:8 by reversed-passive latex agglutination method), and carried the genes stx(2e), estIa and irp2.