It’s a dirty little secret of food poisoning: E. coli and certain other foodborne illnesses can sometimes trigger serious health problems months or years after patients survived that initial bout.

Scientists only now are unraveling a legacy that has largely gone unnoticed.

What they’ve spotted so far is troubling. In interviews with The Associated Press, they described high blood pressure, kidney damage, even full kidney failure striking 10 to 20 years later in people who survived severe E. coli infection as children, arthritis after a bout of salmonella or shigella, and a mysterious paralysis that can attack people who just had mild symptoms of campylobacter.

“Folks often assume once you’re over the acute illness, that’s it, you’re back to normal and that’s the end of it,” said Dr. Robert Tauxe of the Centers for Disease Control and Prevention. The long-term consequences are “an important but relatively poorly documented, poorly studied area of foodborne illness.”

These late effects are believed to make up a very small fraction of the nation’s 76 million annual food poisonings, although no one knows just how many people are at risk. A bigger question is what other illnesses have yet to be scientifically linked to food poisoning.

And with a rash of food recalls – including more than 30 million pounds of ground beef pulled off the market last year alone – these are questions are taking on new urgency.

“We’re drastically underestimating the burden on society that foodborne illnesses represent,” contends Donna Rosenbaum of the consumer advocacy group STOP, Safe Tables Our Priority.

Every week, her group hears from patients with health complaints that they suspect or have been told are related to food poisoning years earlier, like a woman who survived severe E. coli at 8 only to have her colon removed in her 20s. Or people who develop diabetes after food poisoning inflamed the pancreas. Or parents who wonder if a child’s learning problems stem from food poisoning-caused dialysis as a toddler.

“There’s nobody to refer them to for an answer,” says Rosenbaum.

So STOP this month is beginning the first national registry of food-poisoning survivors with long-term health problems – people willing to share their medical histories with scientists in hopes of boosting much-needed research.

Consider Alyssa Chrobuck of Seattle, who at age 5 was hospitalized as part of the Jack-in-the-Box hamburger outbreak that 15 years ago this month made a deadly E. coli strain notorious.

She’s now a successful college student but ticks off a list of health problems unusual for a 20-year-old: High blood pressure, recurring hospitalizations for colon inflammation, a hiatal hernia, thyroid removal, endometriosis.

“I can’t eat fatty foods. I can’t eat things that are fried, never been able to eat ice cream or milkshakes,” says Chrobuck. “Would I have this many medical problems if I hadn’t had the E. coli? Definitely not. But there’s no way to tie it definitely back.”

The CDC says foodborne illnesses cause 325,000 hospitalizations and 5,000 deaths a year. Among survivors, some long-term consequences are obvious from the outset. Some required kidney transplants. They may have scarred intestines that promise lasting digestive difficulty.

But when people appear to recover, it is difficult to prove that later problems really are a food-poisoning legacy and not some unfortunate coincidence. It may be that people prone to certain gastrointestinal conditions, for instance, also are genetically more vulnerable to germs that cause foodborne illness.

For now, some of the best evidence comes from the University of Utah, which has long tracked children with E. coli. About 10 percent of E. coli sufferers develop a life-threatening complication called hemolytic uremic syndrome, or HUS, where their kidneys and other organs fail.

Ten to 20 years after they recover, between 30 percent and half of HUS survivors will have some kidney-caused problem, says Dr. Andrew Pavia, the university’s pediatric infectious diseases chief. That includes high blood pressure caused by scarred kidneys, slowly failing kidneys, even end-stage kidney failure that requires dialysis.

“I don’t want to leave the message that everyone who had symptoms … is in trouble,” stresses Pavia.

Miserable as E. coli is, it doesn’t seem to trigger long-term problems unless it started shutting down the kidneys the first time around, he says. “People with uncomplicated diarrhea, by and large we don’t have evidence yet that they have complications.”

Other proven long-term consequences:

-About 1 in 1,000 sufferers of campylobacter, a diarrhea-causing infection spread by raw poultry, develop far more serious Guillain-Barre syndrome a month or so later. Their body attacks their nerves, causing paralysis that usually requires intensive care and a ventilator to breathe. About a third of the nation’s Guillain-Barre cases have been linked to previous campylobacter, even if the diarrhea was very mild, and they typically suffer a more severe case than patients who never had food poisoning.

While they eventually recover, “We don’t know a great deal about what happens to those people five years later. What does ‘normal’ look like?” Tauxe says.

-A small number of people develop what’s called reactive arthritis six months or longer after a bout of salmonella. It causes joint pain, eye inflammation, sometimes painful urination, and can lead to chronic arthritis. Certain strains of shigella and yersinia bacteria, far more common abroad than in the U.S., trigger this reactive arthritis, too, Tauxe says.

What about other patient complaints?

A variety of other organ problems might be triggered by HUS, that severe E. coli – because it causes blood clots all over the body that could leave a trail of damage, says Utah’s Pavia. Among his hottest questions: HUS patients often suffer pancreatitis. Does that increase risk for diabetes later in life?

But proving a connection will require tracking a lot of patients who can provide very good medical records documenting their initial foodborne illness, he cautions.

Preventing food poisoning