Foodborne illnesses at restaurant chains are rare but can sicken customers, roil businesses

• restaurant chains don't get linked to foodborne illness outbreaks often, but the number of meals they serve causes a lot of concern when contamination of some kind sickens customers.
• Federal health officials identified iceberg lettuce from Mexico served at Taco Bell locations in five states as a source of widespread infections from the diarrhea-causing parasite cyclospora.