Lettuce Help: USDA data on shipments of romaine lettuce can inform foodborne illness outbreak investigations and public health advisories

A study by ERS researchers demonstrates how USDA data on daily shipments of romaine lettuce can be used to determine which producing regions within the United States are free from contamination during a foodborne illness outbreak. The study finds that among the 29 outbreaks of Shiga-toxin producing Escherichia coli (STEC) O157:H7 associated with romaine lettuce between 1998 and 2018, illnesses peaked in April and October, which corresponds with the tail end of the harvest season in the two main romaine growing regions.