«Michele Jay-Russell, a food safety researcher at the University of California Davis who has investigated salad-related poisoning outbreaks in the past, said the raw vegetables that are the most common culprits are basically all salad greens, but especially the chopped and bagged kind.»

Source: https://www.vox.com/science-and-health/2018/4/26/17282378/romaine-lettuce-recall-ecoli-yuma