"a precaution". The MOE employee who spoke to Koebel believed that this meant any adverse samples of Walkerton water were in the past, and filed his subsequent report of the conversation accordingly; Koebel had again failed to note that he was aware of current test results that showed evidence of E. coli and fecal coliforms. Controlling the outbreak Events of May 21 Morning news reports on public radio on May 21 carried a statement by Dr. Murray McQuigge, Walkerton's Medical Officer of Health, reflecting medical investigators' then-current understanding that Walkerton's water system was presumed to be secure and not involved in the outbreak. McQuigge's quoted opinion also characterized E. coli as "unlikely" to be the source of the gastroenteritis outbreak. By 12 p.m. on May 21, however, laboratory results had confirmed enough cases of E. coli O157 in area gastroenteritis patients to merit a declaration by the Bruce-Grey-Owen-Sound Health Unit (BGOSHU) that an infective outbreak existed and was being caused by E. coli O157 contamination somewhere. The Health Unit issued an outbreak number and alerted neighbouring health units of its situation, as well as notifying a variety of Walkerton-centred government and management bodies, including the Walkerton Public Utilities Commission (PUC).1. Shortly after the definitive laboratory results were received, McQuigge, representing BGOSHU, contacted David Thompson, the mayor of Brockton, Walkerton's parent municipality. According to McQuigge, the conversation involved McQuigge alerting Thompson to the fact that community members were falling ill with potentially fatal E. coli infections; according to Thompson, E. coli was not mentioned in the conversation and he was left with the impression that the illnesses presented no imminent threat to public health. Despite their conflicting memories of the conversation, both McQuigge's and Thompson's later testimonies agreed that there had been no request issued that the mayor take action in response to the illnesses; Brockton's emergency plan was not put into action, and Thompson did not contact any public agencies to seek either information or action. Given that the outbreak was continuing and that no reliable information was yet available about the source of the contamination, the BGOSHU issued a cautionary Boil Water Advisory (BWA) to the community, to be distributed via local radio stations only. Local television stations were not contacted about the advisory, nor was national CBC Radio; no paper version of the advisory was distributed to the community that day. Local radio station CKNX-FM, under the impression