Unfortunately, it seems animal agriculture once again cross-contaminated some romaine lettuce. The Public Health Agency of Canada recommends that people in Ontario and Quebec avoid eating romaine lettuce for the time being.
While fruits and vegetables on their own cannot have E. coli, a common source is raw fruits and vegetables that have come in contact with feces from infected animals. Leafy greens, such as lettuce, can become contaminated in the field by soil, water, animals or improperly composted manure.
In addition, a recent study shows that washing contaminated fruits and vegetables is not enough to get rid of the bacteria so we would recommend following the recommendation and avoid romaine lettuce altogether.