A recent outbreak of severe diarrheal illness in the midwest, affecing over 400 people, appears to be related to bagged salad distributed there.
Cyclospora is a parasite that is an unusual cause of diarrhea, but is the definite agent in this outbreak.
This outbreak shows that bagged salad may not be safe, as a general rule. Despite it’s convenience, it’s best to use the real thing and chop it yourself.