Who would’ve guessed sprouts?  Who would have predicted that Germany’s E. coli outbreak, already one of the worst food poisoning epidemics in recent times, might be connected to a food that is virtually a cliché for health foods and vegetarians?

Actually, that might have been the guess of anybody familiar with the recent history of foodborne illness outbreaks, because the experts know those seemingly innocuous raw sprouts can carry toxic bacteria.

In the last 20 years, contaminated bean sprouts, alfalfa sprouts or other varieties have been blamed for at least 40 significant outbreaks of foodborne illness across the U.S., Canada and Europe. Most of those incidents were blamed on Salmonella bacteria, but E. coli contamination has occurred as well.

They include what had been  considered the worst known outbreak of E. coli, a 1996 epidemic in Sakai City, Japan. In that case, nearly 10.000 people, most of them students and teachers served school lunches prepared in a central kitchen, were sickened with E. coli O157:H7.  At least 12 died from kidney failure and related complications.

Eventually, health officials determined the source of the outbreak was radish sprouts, grown on a Japanese farm from seeds that may have come from Oregon. No traces of the offending bacteria were ever found in sprouts.  But, as in other cases where the contaminated food is long gone, epidemiologists determined the cause by a process of elimination.

Japan has since attempted to retrain officials to respond quickly by interviewing victims of outbreaks.

But how would sprouts become contaminated with a toxin associated with cow excrement?

Blame it on healthy growing conditions, according to Dr. John Kobayashi, a veteran epidemiologist in Seattle who now teaches at the University of Washington.

Sprouts pose “an inherent problem” for foodborne illness, Kobahashi explains. If the sprout  seed becomes contaminated — perhaps by cow manure from a neighboring field — the sprouts can become a carrier.  Even worse, they become “an incubator,” he adds. The sprouts and bacteria are nurtured by precisely the same combination of heat and moisture. 

“The juice in the sprout container is inevitably loaded with bacteria, most of which are harmless.”

But if they are contaminated with toxic Salmonella or E. coli, the bacteria grow happily with the sprouts, and may survive a cold water wash.  Because the sprouts are almost always eaten uncooked, there is no “kill step,” no opportunity to heat the food and kill the offending bacteria.

“You could irradiate them,” Kobayashi adds.  “But nobody seems to want that.”

In the case of Sakai City, the problem probably originated with the seeds, he says.  The bacteria gets into the cracks of the seeds.  When the seeds are sprouted, the bacteria thrives. They both end up in somebody’s salad.

 And, a week or so later, somebody gets sick.