Why Lettuce Is Often the Culprit in Foodborne Illness Outbreaks

Salad is typically seen as a healthy choice, but it frequently causes foodborne illness outbreaks. The US is currently facing a cyclosporiasis outbreak in Michigan with over 7,100 cases, likely tied to Taylor Farms iceberg lettuce. This is not an isolated incident: in 2022, romaine lettuce caused an E. coli outbreak linked to Wendy's sandwiches; in 2021, BrightFarms recalled packaged salads after 31 salmonella cases; and in 2020, Fresh Express salad kits were associated with more than 700 cyclospora infections.

The Centers for Disease Control and Prevention estimates that nearly half of reported foodborne illnesses come from produce, with leafy greens at the top. A major reason is that lettuce is the second-most-consumed vegetable in the US after potatoes. Ready-to-eat salad mixes are especially risky because they contain multiple types of greens from different farms. If one type is contaminated, it can taint the entire batch, and since these mixes are distributed widely, contamination can spread far.

How lettuce is grown also contributes to the problem. A 2025 Cornell University study found that E. coli outbreaks in romaine lettuce often originate from irrigation with untreated surface water applied via overhead sprinklers. Switching to drip irrigation could reduce risk but requires investment.

Because lettuce is eaten raw, there is no cooking step to kill pathogens. Its texture—with many crevices and folds—makes it easy for germs to hide. Prewashing in processing facilities doesn't always remove microbes, and cyclospora parasites have thick outer walls that resist most sanitizers. Experts recommend vigorous washing and scrubbing to reduce the risk of ingestion.