The warning signs were faint, and scattered. Something had happened in Pittsburgh in 2000. Something again in Maine in 2001, and then in New Jersey: increased cases of hospital infection. At his offices at the Centers for Disease Control and Prevention in Atlanta, Clifford McDonald pondered the dry jargon of epidemiological reports. Was there a pattern?

Something is now happening in Montreal. This year, a lawyer, Jean-Pierre Menard, noticed a surge in calls from clients whose loved ones had died of infection while in the hospital. For Menard, who specializes in medical malpractice, these were frustrating cases. Responsibility is always hard to prove, an infection hard to trace. But was there a pattern?

The two men in different spots of the continent were among the first to recognize what would soon become a full-blown epidemic, centered in Montreal, a strain of bacterial infection in hospitals that officials believe is particularly dangerous to vulnerable patients.

In the first six months of this year, Clostridium difficile enterocolitis or C. difficile killed 109 patients in 10 hospitals in Quebec and was an accomplice in 108 other deaths, according to conclusions announced two weeks ago by health experts in Montreal.

Officials are unsure exactly how the infection is spreading between hospitals and why it seems to be so deadly, although they have some theories. Public health officials call the deaths alarming. The Quebec health minister labeled the infection a "scourge." McDonald, an infectious disease specialist at the CDC, expects it will spread to other hospitals in North America.

"Based on the experience in Canada, it's a killer. And I think we'll see it more," he said.

For Linda Lanthier, the warnings come too late. Her mother, Lise Langlois, 56, was hospitalized in Montreal in August for a blocked intestine. The surgery went well. Her mother was strong, recovering quickly and happily receiving visitors, Lanthier said.

A few days later, at 4 a.m., Lanthier said she received a call from her mother: "Linda, come. I'm so sick," the woman said. Lanthier rushed to the hospital and found her mother in a room fouled with diarrhea. Lanthier, a dietician at another hospital, said she recognized the symptoms right away: it was C. difficile. Within 48 hours Langlois was in septic shock and her organs were shutting down. In another 24 hours, she was dead.

"It happened so suddenly. I knew people died from this bacteria, but they were elderly. My mother was not elderly. She was strong, still working," Lanthier said. "You go into the hospital for one reason and die of something else. It's scary."

The bacterium has been known for decades to haunt hospitals, officials say. It is typically a threat to patients in hospitals and nursing homes who are receiving strong antibiotics. The antibiotics kill the natural bacteria in the bowels that, in healthy people, easily counteract the toxins of C. difficile. Without that natural defense, C. difficile can explode in the body and eventually overwhelm it.

Typically, the rate of C. difficile infection is low, and few die of its complications. But in an urgent report issued last month, an infection control specialist, Vivian Loo, found twice the normal rate of infection in hospitals in Quebec this year. And death rates rose to nearly 8 percent from the past rate of 1 percent to 2 percent, she reported.

In the first six months of 2004, the bacterium killed as many people in Quebec hospitals as had died from it throughout Canada in the three previous years, her report concluded.

"The incidence and the mortality have gone up. This is an epidemic," she announced at a news conference Oct. 20.

That set off a round of finger-pointing. The C. difficile bacterium is typically spread by the feces of infected people. Quebec's public health system, made up of older hospitals, has undergone budget cuts and staff reductions, and critics say the hospitals are no longer being kept clean.

"The hospital room was dirty, disgusting," said Sophie Mongeon, 31, a Montreal woman whose father was admitted to a hospital last spring because of kidney complications. "There were bloody cotton balls on the floor. The shower was like a campground shower. And I noticed the hand-washing gel in the room was empty; it was never replaced for days."

Her father, Rejean Mongeon, 55, was a "proud, strong man," a veterinarian who was only recently diagnosed with leukemia, she said. As she sat with her father in a hospital in June while he was undergoing chemotherapy, she recalled seeing a television report about the higher incidence of the bacterium at the hospital.

"Oh, boy, that's encouraging," she said her father remarked sarcastically.

A week later, as he was recovering, he developed severe diarrhea. His conditioned quickly worsened. Before he lapsed into a coma, a physician said he was in septic shock, Sophie Mongeon said, and as a veterinarian, he knew that was fatal.

"No one ever told us what was going on," she said. "If we had known about this infection, we would have moved my father. We would have made sure everyone wore gloves and the place was cleaned."

Some experts say hospital staff members who do not wash their hands after dealing with every patient and physicians who over-prescribe broad-spectrum antibiotics are responsible for the epidemic by creating opportunities for C. difficile to grow. Those problems are not confined to Quebec, they say.

Issa Ephtimios, an infectious disease specialist in Toronto, said he quit working at a hospital there after the hospital director ignored his warnings last year that physicians were "giving out antibiotics like candy," which would allow C. difficile to flourish. At least three patients died.

"Those deaths were needless. I truly believe this was physician induced -- something we have done to our own patients," he said in an interview.

Andrew Simor, an infectious disease specialist at Sunnybrook and Women's College in Toronto, agreed. "There's a substantial amount of inappropriate antibiotic usage going on," he said.

At the CDC, McDonald said problems of hygiene and the overprescribing of antibiotics are compounded by the new virility of this strain of C. difficile, called B-I. He and Loo, the infection control specialist in Montreal, independently examined samples of C. difficile and found that the normal strain had mutated and caused outbreaks in Quebec, probably in Pittsburgh and at six other hospitals elsewhere in the United States in 2000 and 2001.

"This strain has an extra toxin, called a binary toxin, that has in the past only been found in 6 percent of U.S. strains, but it is uniformly present in this one. We think it is more virulent, though we haven't proved it yet," McDonald said. "And it has a mutation in a gene that normally suppresses toxin production."

Those two aberrations may make it resistant to some of the antibiotics often used in hospitals, and make it more lethal, he said. McDonald suspects this superbug is present but still unnoticed at other hospitals.

"Some hospitals don't even know they have a problem. We have been trying to make people look at their rates," he said. The CDC is recommending hospitals with outbreaks require all health care workers wear gloves and gowns, stop using rectal thermometers and other shared equipment, return to washing their hands with water instead of alcohol-based gels, clean infected rooms with diluted bleach, and more closely scrutinize the use of antibiotics.

In Montreal, Menard, the attorney, has campaigned with a group for improvements at public hospitals.

Mongeon said she believed the infection rates ought to be made available to the public, so patients and their families can avoid infected hospitals.

"It's not just about my father," Mongeon said. "A lot of people are getting worse in the hospital. I don't want to see it happen to someone else."

Sophie Mongeon holds a photo of her father, Rejean, with his granddaughter before he died of a C. difficile infection.