May 12: Fierce rainstorm hits Southern Ontario and runoff, believed to contain harmful E. coli bacteria, is thought to have polluted Walkerton's water supply. May 12-15: Town residents are exposed to the bacteria, likely through their drinking water. May 15: Greg Patterson, head of A & L Canada Laboratories East Inc., receives three samples, taken that day by Walkerton's Public Utilities Commission marked "Rush, Rush, Rush." All three test positive for E. coli. The lab says it does not know what follow-up measures were taken. A 92-year-old woman dies, but investigators have not confirmed whether her death was caused by the bacteria. May 14-16: The chlorination system at one of the town's three wells, No. 7, isn't working. Lab tests taken from the site show high levels of coliform bacteria, including E. coli. May 17: Patients in local hospitals complain of symptoms including diarrhea, vomiting, cramps and fever. May 17, 18 or 19 (depending who was asked): Walkerton PUC receives test results from the private lab, showing E. coli bacteria in the water. May 19: Mel Dawe, 69, dies one week after his basement was flooded in the storm. Walkerton's water manager, Stan Koebel, assures local health officials the water supply is safe. May 20: Two cases of bloody diarrhea are reported to public health officials by doctors. Walkerton's hospital handles more than 20 cases. May 21: Health officials receive first positive E. coli test results and issue first warning advising the town's 4,800 residents to boil their water. May 22: Lenore Al, 66, a retired part-time librarian, dies at London Health Sciences Centre. May 23: Health officials report 160 people sought hospital treatment and another 500 called hospitals complaining of symptoms. Mr. Koebel discloses results of the town's water tests. Two-year-old Mary Rose Raymond dies. Dr. Murray McQuigge, medical officer of health with the Bruce-Grey-Owen Sound Health Unit, declares the E. coli outbreak the worst in Canadian history. May 24: Robert Brodie, 89, dies after coming in contact with E. coli while staying at a Walkerton nursing home. Edith Pearson, 82, and Vera Coe, 75, also die. May 26: Class-action lawsuit is filed on behalf of those made ill and the families and heirs of those who died, claiming $1-billion in damages. The defendants named are the municipality of Brockton, Bruce-Grey-Owen Sound Health Unit, the Province of Ontario and the PUC. May 29: Laura Rowe, 84, dies just two weeks after moving to Walkerton to live in a nursing home. The Ontario government says it violated its own guidelines when it failed to tell health officials about water contamination detected six weeks before the bacterial outbreak. The government says it knew for years that the Walkerton water system had problems. May 30: After a week in seclusion, Mr. Koebel emerges outside a Walkerton church accompanied by family members and his lawyer.
May 31: Betty Trushinski, a 56-year-old mother of three, dies from E. coli complications. Ontario Premier Mike Harris calls a public inquiry into the E. coli disaster. June 1: Residents learn they may have to wait at least six weeks before they can be sure the town's water supply is free of E. coli. Police confirm as many as 11 people might have died from E. coli-related causes. A total of 784 people have received treatment symptoms and 90 people have been hospitalized. June 2: A report prepared for the Ministry of the Environment finds the most likely source of the outbreak is well No. 7, which had a faulty chlorine-injection system. The Ontario government announces $100,000 in direct relief, which amounts to about $20 a person. June 6: The first of Walkterton's 2,400 students resume classes in schools, churches and community halls in nearby Hanover. June 8: The engineer overseeing the investigation into what caused the contamination says well No. 5, where the chlorination system was working, may have been the source of the bad drinking water.