Here is a chronology of events in the deadly outbreak of E. coli in the southwestern Ontario farming town of Walkerton.

May 12, 2000: Torrential rains wash bacteria from cattle manure into Walkerton's shallow town well. Over the next few days, residents are exposed to E. coli.

May 15, 2000: The town's Public Utilities Commission (PUC) begins drawing water samples.

May 17, 2000: The first symptoms of E. coli begin to surface. Residents complain of bloody diarrhea, vomiting, cramps and fever. It will be two more days before family and emergency room physicians detect a pattern and begin to suspect a public health problem.

May 18, 2000: According to later statements by Dr. Murray McQuigge, the medical health officer for Grey-Bruce, the PUC receives a fax from a lab confirming E. coli contamination from the May 15 samples. But water manager Stan Koebel fails to notify the Ministry of the Environment or the public health office.

May 19, 2000: The Region's Medical Health Office (MHO) receives word of several patients with E. coli symptoms. Over the next few days, the public health office makes repeated calls to the utility asking if the water is safe. According to McQuigge, the utility says there's no problem.

May 21, 2000: Region's MHO begins independent testing of the water and issues a boil-water warning.

May 22, 2000: The first death directly linked to E. coli is reported.

May 23, 2000:  Health officials receive confirmation from their own tests that Walkerton water is contaminated with E. coli. By now, more than 150 people are reported to have sought hospital treatment, while another 500 complain of symptoms. A two-year-old girl dies.

May 24, 2000: Dr. McQuigge, declares this Canada's worst outbreak of E. coli. More cases are expected, as E. coli can have an incubation period of up to 10 days, and can be spread from person to person.

May 25, 2000: McQuigge informs the media that that the PUC had not acted on an earlier fax from a lab confirming E. coli contamination from the May 15 samples. He alleges his office was "clearly misled" about Walkerton's water.

May 26, 2000: The first funeral is held as then Ontario Premier Mike Harris denies Tory government cuts are to blame for the tragedy. The Ontario Provincial Police announces it is investigating events in Walkerton, as some townspeople launch a class-action lawsuit.

May 31, 2000: Facing heavy criticism over the province's role in water safety, Harris orders a public inquiry into the tragedy. By now, six people have died.

June 12, 2000: A house-by-house disinfection program begins, as Walkerton starts cleaning up. Pipes are scrubbed as chlorinated water is pumped through 2,500 customer locations. Throughout the summer months, during this arduous process, Walkerton remains under a boil-water order.

June 27, 2000: The federal government announces it will invest almost $10 million to find better ways to treat Canada's water and wastewater

July 13, 2000: Dr. Murray McQuigge says no new cases of E. coli sickness have been reported since June 9. He says Walkerton's health crisis is over, but the boil-water advisory will remain in place for months to come.

July 25, 2000: A seventh person dies from E. coli.

July 28, 2000: The Ontario Environment Ministry releases a list of 131 municipalities with "deficient" water facilities and announces a plan for upgrades. Among them, urban centres like Hamilton, Peterborough and Sudbury.

Aug. 26, 2000: New drinking-water laws take effect in Ontario.

Oct. 16, 2000: Public inquiry under Justice Dennis O'Connor begins.

Nov. 16, 2000: The province declares Walkerton's water supply safe, but lets the health office deal with lifting boil-water advisory.

Nov. 17, 2000: Stan Koebel resigns, after negotiating a $98,000 severance package, including $34,000 to cover vacation time. Walkerton council agrees on April 23, 2001, to pay Koebel $82,000 in severance and vacation plus $5,000 in legal costs.

Dec. 5, 2000: The boil-water advisory is finally lifted by the health unit, still leaving some residents unsure whether it's safe to resume drinking tap water.

Dec. 6-7, 2000: Stan Koebel's brother, Frank, who was Walkerton's water foreman at the time of the outbreak, stuns the inquiry with testimony about drinking on the job and routine falsification of safety tests and records.

Dec. 18, 2000: Stan Koebel begins his testimony at the inquiry by apologizing for his role in the tragedy. He confesses he didn't really know what E. coli was, or its health effects.

Dec. 19, 2000: Koebel tells the inquiry that water tests and water safety reports for the Ontario government were routinely falsified for about 20 years. He also testified that provincial officials knew the town wasn't meeting minimum standards for water testing.

March. 19, 2001: A class-action settlement is approved for the residents of Walkerton. The settlement provides at least $2,000 for everyone affected by the E. coli outbreak, with all higher claims to be assessed individually, with no cap.

Mar. 27, 2001: The Ontario government delivers a $15-million cheque to the town of Walkerton to cover costs associated with the E. coli outbreak. Two-thirds of the money will go to restoring the municipal water supply, tainted by the deadly bacteria. The other $5 million will pay off the loans the municipality took out to deal with the crisis.

April 23, 2001: Municipal politicians in the town of Walkerton vote to pay out most of a controversial $98,000 severance package to Stan Koebel.

June 17, 2001: Gov. Gen. Adrienne Clarkson pays tribute to the victims of Walkerton's tragedy by unveiling a memorial stone.

June 25, 2001: Dr. Richard Schabas, former medical officer of health, tells the inquiry he repeatedly warned the Ontario government that funding cuts would compromise public health.

June 26, 2001: Brenda Elliott, former Ontario environment minister, tells the inquiry the government acted as a team when making decisions around funding cuts.

June 27, 2001: Norm Sterling, also a former environment minister, testifies senior bureaucrats assured him that any risks to public health caused by layoffs and budget cuts were manageable.

June 29, 2001: Then-premier Mike Harris tells the inquiry that he was never warned that budget cuts could lead to serious health risks.

Aug. 15 - 17, 2000: In its closing arguments, government lawyers blame the E. coli tragedy on the "reckless" practices of former water manager Stan Koebel. However, Koebel insists the blame must be shared with the Ontario government.

Nov. 26, 2001: A study finds the total cost to clean-up and fix the Walkerton water problem will be at least $64 million. It adds that the number skyrockets to $155 million when human suffering from the tragedy is factored in.

Jan. 14, 2002: O'Connor delivers the final Walkerton report to the Ontario government, one week before it is to be released to the public.

Jan. 16, 2002: Fury erupts over the leaking of the Walkerton inquiry report five days before it is to be officially released to the public.

Jan. 18, 2002: Justice Dennis O'Connor's report concludes the tragedy was preventable. It says the Koebel brothers' shoddy work and dishonesty, along with government budget cuts and Environment Ministry ineptitude, were to blame.

May, 2002: O'Connor delivers the second part of his report to the Ontario government.

Aug 20, 2002: The province releases draft regulations under the Nutrient Management Act to protect provincial drinking water.

Nov. 23, 2002: An arbitrator awards former public utilities foreman Frank Koebel a $55,000 compensation package by the municipality for his job loss.

Dec 5, 2002: Study finds that most who fell ill from E. coli infection have recovered, although hundreds still suffer from gastrointestinal problems.

Dec. 22, 2002: Ontario study finds half of provincial water plants are still violating safety laws implemented after the tainted water tragedy.

Feb. 18, 2003: Opposition parties call for the resignation of Walkerton-area Conservative politician Bill Murdoch for suggesting Tory government bears no responsibility for disaster. Murdoch refuses to apologize.

April 23, 2003: Charges of common nuisance, fraud and breach of trust announced against Stan and Frank Koebel.

Nov. 30, 2004: Koebel brothers plead guilty to common nuisance endangering lives, health and safety of the public with maximum two-year sentence. Victims tell court about personal impact of the tragedy.

Dec. 1, 2004: Defence asks for conditional discharge. Crown asks for close to maximum jail time for Stan Koebel, conditional sentence for Frank Koebel.

Dec. 20, 2004: Stan Koebel is sentenced to one year in jail, Frank Koebel to nine months of house arrest. The ruling is met with absolute silence in the courtroom. In sentencing, Ontario Superior Court Justice said "the offenders are not being sentenced for being the cause of the Walkerton water tragedy.''

With files from Canadian Press