Foodborne Outbreaks Associated with Leafy Greens
This year at the International Conference on Emerging Infectious Diseases, one of the topics was foodborne outbreaks in the United States associated with leafy greens. A leafy-green-associated foodborne outbreak was defined as two or more illnesses due to the consumption of a single leafy green food item (lettuce, cabbage, mesclun mix, spinach) or a salad item containing one or more leafy greens. According to CDC data, of 10,421 foodborne outbreaks reported during 1973-2006, 502 (4.8%) outbreaks, 18,242 (6.5%) illnesses, and 15 (4.0%) deaths were associated with leafy greens. Norovirus was responsible for 196 (58.3%) outbreaks; Salmonella, 35 (10.4%) outbreaks; and E. coli O157:H7, 30 (8.9%).
The following is some additional information from the conference regarding leafy-green-associated foodborne illness:
- The median size of leafy green-associated outbreaks (18 illnesses) was twice the median size of non-leafy green-associated outbreaks.
- During 1986-1995, U.S. leafy green consumption increased 17.2% from the previous decade. During the same period, the proportion of all FBDO due to leafy greens increased 59.6%.
- During 1996-2005 leafy green consumption increased 9.0% and leafy green-associated outbreaks increased 38.6%.
- In 296 (69.4%) outbreaks, leafy greens were served at a restaurant.
- 11 (2.2%) involved cases in multiple states.
From 1986 through 2005, the number of leafy-green-associated foodborne outbreaks associated with lettuce rose at a much higher rate than can be accounted for by an increase in leafy green consumption. Over half of the leafy-green-associated foodborne outbreaks involved restaurants.
In May there was a lettuce-associated E. coli outbreak in the state of Washington. As with most of the previous leafy-green-associated foodborne outbreaks, the lettuce was served at a restaurant and other eating establishments (in this case, a school cafeteria). Read our press release entitiled, “E. coli Outbreak Associated with Lettuce Prompts Call for Better Sanitation.”