“During its journey from farm to table, there are many opportunities for harmful microbes to invade.
As the largest cyclospora outbreak in U.S. history wanes, experts have said it's probably safe to eat salad again. But some people have become wary of prepackaged lettuce -- which is often chopped, mixed, cleaned and vacuum-sealed in far-off places, and has traveled long and sometimes circuitous distances to get to your grocery store.
Most of the time, that lettuce arrives on the shelf safe to eat. Yet there are many points along its journey that it can pick up pathogens like E. coli, listeria and, of course, cyclospora.
Leafy greens are among the most common sources of food-borne illness outbreaks in the United States. Here's a look at vulnerabilities in the food system that can make those outbreaks happen.
Cultivation
The most vulnerable time for lettuce is when it's being grown and harvested on a farm.
1. Water exposure
The water used to irrigate, fertilize or apply pesticides to lettuce is a frequent source of contamination. Leaky septic tanks, wastewater treatment plants and latrines can contaminate that water with microbes like E. coli or cyclospora. Heavy rain can also cause fecal matter from nearby livestock farms to leach into the water supply, though there are typically buffer zones in place.
Water used for produce sold in the United States must be tested for E. coli, which can signal fecal contamination and set off other testing. That water does not need to be tested for cyclospora.
2. Fertilization
Manure is often made from animal waste and can contain pathogens if it has not been properly treated. Most growers of lettuce sold in the United States must use manure that has been heat-treated to kill harmful microbes. Larger growers often avoid manure completely by opting for chemical fertilizers instead.
3. Wildlife encounters
Bacteria like E. coli and salmonella can latch on to lettuce from tainted soil or from droppings from animals like birds, pigs and deer. To reduce, but not always eliminate, those contaminants, farmers typically discard any crops that are growing near visible hoof prints or animal droppings, and they strip the outer layers of leaves on lettuce heads during harvesting.
4. Harvesting
Lettuce is typically picked by hand, in some cases on farms with inadequate bathroom facilities that may lack soap, toilet paper, running water or paper towels. If a field worker has a stomach bug and cannot wash their hands after using the bathroom, they might unwittingly transfer a pathogen like cyclospora onto the lettuce. Harvesting knives can also spread pathogens from one head to another.
Processing
Lettuce is cut, washed and mixed before bagging, potentially spreading pathogens from one lettuce head to multiple bagged salads.
5. Cutting
When lettuce is chopped or shredded into smaller pieces, any pathogens that are present (from a contaminated head of lettuce, for instance, or from dirty chopping equipment) have more surfaces to cling to and feed from.
6. Washing
Labels like ''pre-washed'' and ''triple washed'' on bagged lettuce mean that it has been cleaned, often in a trough-like machine that tumbles the lettuce through flowing water to dislodge any soil or other debris, and through a food-safe sanitizing solution to kill microbes.
If there is too much debris in the water, the chemicals can't kill all of the pathogens -- and the standard chemicals in these solutions, like chlorine, don't kill cyclospora.
7. Mixing
Lettuce mixes and ready-to-eat salad kits sometimes include leafy greens and other vegetables like cabbage and carrots that are sourced from multiple farms. If a pathogen is present on produce from a single farm, it might get mixed into many individual bags.
Distribution
Bagged salad must survive sometimes harsh shipping conditions before it reaches a restaurant, supermarket or your plate.
8. Refrigeration
Most bacteria and parasites thrive in warmer temperatures, so lettuce must be continuously refrigerated -- including at delivery docks and in trucks, grocery stores, restaurants and homes. But sometimes those refrigerators aren't cold enough or are broken, or produce is accidentally left outside in the heat or on a kitchen counter.
9. Preparation
The final vulnerable moment for bagged lettuce is right before you eat it. Perhaps a restaurant worker with norovirus prepares a salad with unwashed hands, or you chop lettuce with a knife you used on raw chicken.
Rinsing fruits and vegetables under running water can reduce, but not eliminate, some pathogens -- including cyclospora, which can be killed only by heating.
Sources: Randy Worobo, a professor of food safety microbiology at Cornell; Lee-Ann Jaykus, a professor emerita of food microbiology and safety at North Carolina State University; Haley Oliver-Jischke, a professor of food science at Purdue University; Amanda Deering, an associate professor of fresh produce safety at Purdue University; Ben Hartman, founder of Sungold Consulting; Kristin Kiesel, a professor of agricultural and resource economics at the University of California, Davis
This article appeared in print on page D7.” [1]
1. For Lettuce, Going From Farm to Plate Is Perilous: [Science Desk]. Caroline Hopkins Legaspi; Draper, Kevin; Fadanelli, Morgane. New York Times, Late Edition (East Coast); New York, N.Y.. 25 Aug 2026: D.7.
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