I have a new column up at Scientific American about a health issue that is really just starting to be discussed: Whether foodborne illness causes long-term health problems, and therefore whether it should be a higher medical and public-health priority than it is now.
Quick summary: The few studies that have followed victims of foodborne illness for years afterward show that later in life, they suffer higher-than-usual rates not only of digestive trouble, but of arthritis and kidney problems, as well as greater risk of heart attack and stroke.
I start the story with the tale of a Florida teen named Dana Dziadul, who 11 years ago was hospitalized with Salmonella and now at 14 has what is called “reactive” arthritis. Her mother Colette struggled for years to figure out why this was happening to her daughter, but didn’t put the pieces together until she was asked to complete a survey of foodborne illness survivors, and spotted a list of possible after-effects — sequelae, technically — that the surveyors were curious about. That caused her to go back into Dana’s medical chart, where she realized that her daughter’s joint problems actually began while she was hospitalized as a 3-year-old.
From the story:
A survey of 101,855 residents of Sweden who were made sick by food between 1997 and 2004 found, for instance, that they had higher-than-normal rates of aortic aneurysms, ulcerative colitis and reactive arthritis. A review of a major provincial health database in Australia revealed that people there who contracted any bacterial gastrointestinal infection were 57 percent more likely to develop either ulcerative colitis or Crohn’s disease, another chronic bowel condition, than people born in the same place and era who had not had such infections. And several years after a 2005 outbreak of Salmonella in Spain, 65 percent of 248 victims said they had developed joint or muscle pain or stiffness, compared with 24 percent of a control group who were not affected by the outbreak.
The challenge of proving this connection is that our system for investigating foodborne illness is not set up for tracking victims long afterward. That’s first because state health departments, which bear the burden of identifying outbreaks, are most concerned with finding people at the time, not keeping track of them; and second, because many outbreaks are spread across multiple states, with only a few victims in each state — so that maintaining contact with former victims would require a shared effort that no one is set up, or funded, to do. (That’s not even to mention the complication of people moving from one jurisdiction to another. Myself, for instance, I’ve moved five times in the past 10 years.)
One of the few studies to make a strong case for these aftereffects was based on a research project in which victims were identified at the time, and tracked afterward, precisely because their outbreak was so unusual and so big. In May 2000, the water supply of Walkerton, Ont. became contaminated with E. coli O157:H7 after heavy rains washed cow manure into the local aquifer and the water-purification system was overwhelmed. Much of the town’s roughly 5,000-person population became at least mildly ill, and in many cases gravely ill. (I covered the Walkerton outbreak at the time; you can read my first story here. [NB, that’s .pdf that will download; the original is behind a paywall.])
In response, the Ontario government set up the Walkerton Health Study to medically assess the aftereffects going forward — making what they were doing a prospective study, one of the stronger study types in public health. From my column:
In 2010 the study published its findings: compared with residents who did not get very sick, those who endured several days of diarrhea during the outbreak had a 33 percent greater likelihood of developing high blood pressure, a 210 percent greater risk of heart attack or stroke, and a 340 percent greater risk of kidney problems in the eight years following the outbreak.
Those outcomes were not limited to people who developed the most serious consequences of E. coli O157 infection. Even Walkerton residents with milder symptoms experienced circulatory problems that would not have been linked to E. coli without the prospective monitoring. That discovery suggests how common the late-onset effects of E. coli infection might be, says William F. Clark, the study’s leader and a professor of nephrology at the University of Western Ontario. Clark recommends that survivors of such illnesses have their blood pressure checked every year and their kidney function checked every two or three years.
Here’s the ultimate TL;DR from these studies. We already know that foodborne illness is an enormous problem, with 48 million cases per year in the United States. But for the most part we do not make those a very high public health priority, because most of the cases resolve on their own after an unpleasant few days staying close to a bathroom.
But if the toll of foodborne illness is not just a few days of lost productivity at the time, but rather extended medical care for chronic health conditions, than we have underestimated how much foodborne illness costs us, and society as a whole. And that suggests that perhaps we should be doing a better job of preventing it to start with, in order to prevent the lost years of activity and health care spending that occur years afterward.
By a coincidence of timing, one of the groups mentioned in my column, the Center for Foodborne Illness Research and Prevention, is holding a conference May 14 in Durham, NC, about this issue. For more information, go here.