UPDATE 1-E. Coli Kills Three, Infects 500 in Canada...05/25/00

TORONTO, (Reuters) - An infant and two elderly people are dead, 20 others have been hospitalized and a further 500 may be infected in Canada's worst outbreak of E. coli bacteria, health officials said Wednesday.

Authorities said the outbreak in Walkerton, Ontario, a town of about 5,000 people about 200 kilometers (125 miles) northwest of Toronto, had reached "epidemic proportions".

"There has never been this kind of number of cases (in Canada)," Murray McQuigge, chief medical officer at the Bruce and Grey counties' health unit, told Reuters.

McQuigge said an infant and an 82-year-old woman died Wednesday and at least half of the 20 people admitted to hospitals were in critical condition. A health official said another elderly person had died Wednesday but the official said she did not know the age or gender.

Eight children were being treated at Children's Hospital of Western Ontario, in London, Ontario, said Julie Troyano, a hospital spokeswoman.

E. coli (Escherichia coli) is usually found in the intestines of humans and animals. Some strains cause dangerous, even life-threatening, infections.

Symptoms include fever, severe cramping, diarrhea and vomiting. It can take two to 10 days for symptoms to appear and normally about a week to recover.

Doctors were unsure what had caused the E. coli outbreak. However, it is believed the bacteria might have found its way into the town's water supply after heavy rains two weeks ago.

Five investigators from the Ontario Ministry of Environment were investigating the cause of the outbreak.

"We want to make sure we all the answers before we jump the gun on anything," said Dan Newman, the province of Ontario's environment minister.

"I don't think we ought to be pointing fingers at anyone or anything at this time but focus on the people of Walkerton," Newman told a news conference.

He said the investigators would release their conclusions "shortly", but did not elaborate.

Meanwhile, Walkerton residents were being told not to even wash their hands unless the water was boiled or treated with chlorine.

"We are not going to lift the water advisory until the environment ministry assures us that everything is okay," McQuigge told Reuters.

McQuigge said health officials were alerted to the outbreak Friday by a pediatrician in a nearby town who had seen two cases of bloody diarrhea.

By Sunday, McQuigge said his office received the first positive culture for E. coli 0157 taken from a patient with bloody diarrhea.

"The concern is seven to 10 per cent of people with E. coli 0157 may develop kidney complications about nine days after," McQuigge said. "This is especially a concern in the very young and the elderly. There is a death rate of 1 to 3 percent."

McQuigge added: "We are saying do not use antibiotics to treat these cases. Preliminary evidence shows that using antibiotics to treat E. Coli can cause kidney failure."