Salad usually such as healthy eating. Except now, as the US is dealing with a growing outbreak of cyclosporiasis that has sickened more than 7,100 people in Michigan alone, possibly caused by iceberg lettuce supplied by Taylor Farms.
In fact, leafy greens are often implicated in foodborne illness situations. There were 2022 multistate E. coli An outbreak tied to romaine served in Wendy’s sandwiches and 173 cases of norovirus linked to Illinois eatery DC Cobb’s. In 2021, BrightFarms recalled mixed salad greens sold in several states after 31 people contracted salmonella. And in 2019, 167 people were infected with the virus E. coli after eating romaine harvested in the Salinas Valley region of California. This isn’t even the first cyclospora outbreak linked to lettuce: In 2020, Fresh Express salad kits were linked to more than 700 cases of human infection.
The Centers for Disease Control and Prevention estimates that produce is responsible for nearly half of all foodborne illness cases, with leafy greens topping the list. So what makes lettuce the biggest source of American stomach problems?
One major reason is simply that many people eat it. Lettuce is the second most consumed vegetable in the US after potatoes. (The latest outbreak confirms that the potato will always be the king of the US vegetable. Plus, french fries.) Wraps, subs, tacos, you name a fast food sandwich and it probably has lettuce on it. Salad dressing chains are a staple all over the US. Grocery store shelves are full of salads, on top of unadorned heads of iceberg lettuce and bowls of spinach.
Those ready-to-eat salads and spring mix mixes pose the greatest risk because they contain many types of leafy vegetables, which can come from different farms and locations. If one type of lettuce in the mix is contaminated, it can contaminate the entire bag. And because contaminated lettuce is packaged in a large salad bag, it has the potential to spread germs far and wide.
How lettuce is grown can also expose it to a variety of pathogens. A 2025 study by Cornell University researchers studying E. coli The romaine lettuce outbreak found that most of the contamination comes from irrigation with untreated surface water used by overhead sprinkler irrigation systems. There are ways to reduce that risk, including switching to irrigation systems that don’t directly touch the leaves, but that would require optimization and downtime.
Satisfying lettuce is what makes it prone to harmful bacteria. Since it’s eaten raw—who really wants boiled lettuce? Like other fruits and green products, green leaves do not go through what is known as a “killing step”—heating, pasteurization, or freezing—designed to kill bacteria during food production.
The texture of lettuce is an additional factor in its ability to spread disease. “Most types of lettuce have many cracks and folds,” says Jeanne Marrazzo, CEO of the Infectious Diseases Society of America. “It’s very easy for these little bacteria to get in there.”
Even pre-washing processes in production facilities do not remove the bacteria, which can cling firmly to the leaves. In the case of cyclospora, the parasite has thick outer walls, making it highly resistant to many food disinfectants. Experts say vigorous bathing that includes scrubbing is the best way to get rid of cyclospora.
“If you don’t wash these products properly, you’ll end up ingesting anything,” said Amira Roess, an epidemiologist at George Mason University.
