The thick, black binder that Paula Gillett keeps charts her son Jack's battle last year against a food-borne illness caused by E coli.

CHICAGO — The thick, black binder that Paula Gillett keeps charts her son Jack's battle last year against a food-borne illness caused by E. coli. Filled with medical records, meal calendars and other papers, the binder documents Jack's initial illness, the kidney failure that struck next and his eventual recovery.

What is not in Gillett's binder — and what Jack's doctors and state and local health department officials could never determine — is the source of the E. coli that caused his illness, kept Jack in hospitals for three weeks, and led to 13 dialysis treatments and six blood transfusions.

"Do I want somebody to be mad at? Maybe," Gillett said during an interview at the family's Rockford, Ill., home. "I just want to know how this happened to my son. I want to have the knowledge."

Her 9-year-old son's ordeal and the lack of certainty about what caused his illness illustrate two troubling, though not widely known, aspects of food-borne illness. Even as tainted food causes thousands each year to endure long-lasting illnesses, health agencies are having a difficult time finding the cause of the problem, and a push is on at the federal level to better trace suspected pathogens.

Conventional wisdom holds that food-borne illnesses are mostly minor and short-lived. And while the vast majority of victims do not see a doctor, blaming their symptoms on a routine virus, some victims experience serious and long-lasting medical consequences such as kidney failure or paralysis. Of an estimated 76 million food-borne illness victims each year, some 300,000 are hospitalized and close to 5,000 die.

"There's a real misconception about how serious a food-borne illness can be," said Susan Vaughn Grooters, public health specialist at Safe Tables Our Priority, or S.T.O.P., a food safety group based in Northbrook. "Who really thinks that a hamburger can paralyze somebody?"

It also is often assumed that the cause of these illnesses is eventually tracked down — and often connected to a major outbreak, like the ones that tainted spinach in 2006 and caused three deaths. In fact, in nearly 60 percent of outbreaks, a source of the pathogen is never found; the illness remains a public health mystery, according to the Centers for Disease Control and Prevention.

In cases not tied to an outbreak, determining the source of a pathogen can prove even tougher. It is difficult, if not impossible, to recall a week of meals and snacks eaten during a food-borne illness's incubation period, much less find what remained from the tainted meal or unused ingredients to test.

"Really, the only time you nail these things down with any satisfaction is when you have a really, really large outbreak," said Dr. Glenn Morris, the director of the Emerging Pathogens Institute at the University of Florida. "With an individual patient, it's exceedingly difficult to identify the source."

There are obstacles to identifying the food source of a pathogen throughout the food safety system. While molecular fingerprints of the pathogen, taken by lab workers, help identify it, they can only link victims if the suspected food has not been found for a molecular comparison.

And in cases like Jack's, where there appears to be one victim, it is nearly impossible to identify the tainted food.

Food safety advocates say a quicker response to illnesses may help identify sources, as would better tracking of food through the manufacturing process.

In an effort to find ways to better trace tainted food, officials from the Food and Drug Administration and the Department of Agriculture will hold a public meeting next month to search for solutions. Better tracking mechanisms also are included in pending food safety legislation.

Among the other goals are improving communication between hospitals and local and state health officials, as well as between state health departments when an outbreak crosses state lines.

"People just aren't communicating the way a good system should be. We'll never be able to figure out how to prevent long-term consequences if we don't know what's making them sick," said Vaughn Grooters.

Over the course of three weeks in two hospitals, Jack had 13 dialysis treatments and six blood transfusions, according to his mother and the medical records she has maintained.

Jack's odyssey with a food-borne illness began in July 2008, when he accompanied his parents on a three-day driving trip through Illinois and Indiana to Kentucky, where Jack's father, Bruce, had business.

Along the way the family stopped at restaurants, including fast-food places, and stayed in a motel. One night, Jack and his father had a bout of diarrhea, but it was over quickly, and Gillett assumed it was just a virus. When they returned to Rockford, Jack again had diarrhea and also was vomiting, had a fever and pain on his right side. His mother feared the 9-year-old's appendix was inflamed.

Gillett took Jack to the doctor, but the doctor said Jack had a bug and told Gillett not to worry. When Jack continued to decline, and after he had bloody diarrhea, the family took him back to the doctor. He then went to the hospital, and E. coli was identified as the cause of his illness. Jack was transferred to a hospital in Madison and, as his kidneys failed, placed in an intensive care unit.

While Jack was being treated, Gillett was bedside with a laptop, searching the Internet for clues to how he might have gotten sick. She suspected that his illness might be linked to a recall around the same time of more than 5 million pounds of meat produced for ground beef, but no connection could be found.

Officials eventually linked that tainted meat to 41 illnesses in Ohio and Michigan.

"I was racking my brain trying to figure this out," Gillett said.

Today, Jack is a healthy 5th grader who likes soccer and golf, playing with Lego and his dog Bandit. Though he was recently allowed to stop taking medication for high blood pressure, his parents keep an eye on it, and he still undergoes regular blood and urine tests.

But his illness also has changed the way the family lives — something experts say is common among victims of food-borne illnesses. Jack, for instance, never eats beef that is not cooked by his mother, and he will not eat fast food except at a nearby restaurant that the family believes is clean and follows safe food-handling practices. He generally orders a chicken dish instead of his fast-food favorite, cheeseburgers.

Gillett also cooks beef longer than she did before Jack was stricken — "Now there's no pink," she said — and in the kitchen she keeps a meat thermometer close by. She calls it her "best friend."

"We think about this when we eat, and we think about it when we feed him," she said of the illness. "I had no idea how bad it could be. We're really so lucky this wasn't worse."

Elica Faye Williams-Bohnert was not so lucky. She became ill from E. coli in October 2001, not long after her third birthday. As with Jack, the strain of E. coli that struck Elica is usually found in ground beef, and doctors initially thought that some minor bug was responsible.

Julie Bohnert also thought her daughter's illness would be over relatively quickly. Instead, it turned into an extreme case.

"They told us that it was E. coli, and I thought it would run its course and we would go back to living our life," Bohnert said. "But it didn't turn out that way. It really changed our life."

At one point, Elica went into cardiac arrest, and her parents were told to gather the family at the hospital to say goodbye. She recovered, however, and after six months in a hospital and another six months at a rehabilitation center, she went home. She spent about four months on dialysis.

Bohnert suspected Elica became ill after the family ate at a Mexican restaurant near their home in St. Mary, Mo. But, she said, health department officials did not try to find the source of the pathogen because Elica's case did not appear to be part of a larger outbreak.

Now 11, Elica faces many challenges after a kidney transplant and a series of strokes that left her weak on the right side of her body. Elica takes 16 medications a day to help control her seizures and deal with other medical issues. A 5th grader, she attends special-needs classes at a public school. She cannot speak much, but she has a keen understanding of what others say, her mother said.

In spite of it all, Bohnert said, family members feel fortunate that they did not lose Elica.

We're just happy to have her," she said. "We'll take whatever we have."