A WARNING ABOUT THE MENACE OF LETTUCE.
How important is lettuce to you? When romaine lettuce disappeared from the grocery shelves last week after an urgent plea from food-inspection agencies in Canada and the U.S., I think we were all left rethinking the role of produce in our lives. When my body revolts against my usual diet of flesh, and signals that I need something green in a larger quantity than a side of guacamole, I usually don’t involve lettuce. Probably I’ve inherited rural prejudices from my ancestors. Lettuce isn’t food; it’s the food we feed food.
Still, I couldn’t help feeling sad at the enormous void left in the produce section by the Canadian Food Inspection Agency’s emergency bulletin. Even I will buy a fancy bagged salad from time to time, out of a bachelor’s pathetic sense of adventure. And let’s face it. The Platonic ideal of a hamburger has to include a lettuce leaf. If lettuce were wiped off the Earth for good and all memory of it lost to mankind, we would know at a deep, intuitive level that something was missing.
Enough esoteric sciencefiction horror, Cosh, I hear you saying: but we cannot avoid science-fiction horrors in discussing the latest outbreak of Escherichia coli O157:H7 in romaine lettuce. A sci-fi menace is pretty much just what this subtype of the E. coli bacterium is. Indeed, it is a celebrity among pathogens: it was O157:H7 that caused the U.S. Jack in the Box outbreak of 1993, which killed four children and remains the most notorious incident of food-borne illness in that country’s history. (One of the kids got it through person-to-person transmission at a daycare, and had never eaten a hamburger.)
This serotype of E. coli, with a deviousness that only evolution can devise, produces toxins that attack the gut and kidney. Treatment with antibiotics is actually suspected to make it work faster, and anti-diarrhea medications merely help it to stay put in the friendly confines of the G-I tract.
Most of the time, of course, even O157:H7 won’t kill you. When it comes to food-borne illness, the folk understanding you probably share with me is true: you have a lot more to worry about from the dangers of undercooked meat and poultry. Still, it is a fact, or at least it is the best guess of epidemiologists, that plants cause more than half of illness associated with foodborne outbreaks in the U.S. every year, and leafy vegetables like lettuce are the main culprit within that category. Most of those bouts of sickness involve norovirus, and are not too severe: when you count hospitalizations, land animals pull slightly ahead of plants, and once you get to deaths, meat and poultry are far ahead.
But romaine lettuce has undoubtedly had a bad year. In December 2017 there was an outbreak of H7 in Eastern Canada and the U.S. that sent 26 people to hospital and killed two, one on either side of the border. The food investigators who do “tracebacks” on outbreaks — whose speed and thoroughness are a contrast to almost everything else in food science and regulation — did not make much headway with this outbreak. The illnesses on both sides were caused by the same bacteria, but in Canada the problem seemed obviously connected with romaine lettuce, while in the south the evidence was hazier. The investigators were unable to follow the trail back to a specific area.
A larger H7 outbreak happened in April of this year, hospitalizing 96 Americans and killing five, and the clues this time were pointier. Romaine was definitely to blame, and samples taken from patients were successfully matched with a specific 3.5-mile patch of an irrigation canal in Yuma County, Ariz. Such Sherlockian detection is typical of the FDA and the CDC, and sometimes they can chase a food-borne pathogen right up to the gate of a particular farm.
ROMAINE LETTUCE HAS UNDOUBTEDLY HAD A BAD YEAR.
In this case, there was a murder scene but no smoking gun. Having tied the problem to a very specific locale, the traceback teams could not offer much in the way of new useful advice to lettuce growers or nearby feedlot owners. There were too many possible paths from cow-pat to canal to crop. No one was obviously to blame. Killing floors operate year round, but in the Case of the Tainted Lettuce, the end of the growing season had eliminated much of the evidence.
That may have been a factor in the fast, almost unprecedented directive that took romaine lettuce off Canadian and U.S. shelves last week. Gene evidence suggests that this year’s O157:H7 bacteria are related to last winter’s mysterious ones, but not the Yuma strain from this spring. On Monday the source of the pathogen was officially tied down to lettuce grown in the Central Coast region of California, leaving us all free to purchase and eat romaine from elsewhere while the focus of investigation narrows. The last case of illness was reported on Oct. 31, and any new illness would probably have emerged already in the meantime. You have the all-clear to eat romaine lettuce — should you, for some reason, care to.