STEC infections linked to leafy greens more likely to occur in spring or fall
Outbreaks of Shiga toxin-producing Escherichia coli that are linked to leafy greens are more likely to occur in the spring or fall, even though leafy greens are grown year-round in the United States, study findings showed.
The illnesses are often severe and widespread, researchers reported in Emerging Infectious Diseases. Among leafy greens, romaine lettuce causes more than half of the outbreaks.
“Infections with Shiga toxin–producing Escherichia coli (STEC) bacteria cause an estimated 265,000 illnesses and cost $280 million in the United States each year,” Katherine E. Marshall, an epidemiologist in the CDC’s Outbreak Response and Prevention Branch, and colleagues wrote in Emerging Infectious Diseases.
Marshall and colleague STEC outbreaks that were tied to leafy greens from 2009 to 2018 in Canada and the U.S. Toutbreaks 1,212 illnesses, deaths and 77 instances of hemolytic uremic syndrome.
54% of outbreaks were linked to romaine lettucehe majority of outbreaks occurr in the fall (45%) and spring (28%). nvestigators’ efforts to evaluate the processing and growing of greens linked to outbreaks via traceback investigation of the food supply chain were often unsuccessful.
Theleafy greens were the most common cause of foodborne STEC outbreaks, the most common being ground beef.
“Knowledge gaps remain, including the drivers of the seasonality of leafy green outbreaks, and knowledge of why outbreaks are disproportionately linked to romaine lettuce,” concluded. “Investigators should work with federal and state health partners, the research community, the leafy green industry and retailers to fill these knowledge gaps and collect additional information. Additional efforts should include identifying data points that would improve traceability of leafy greens during outbreaks. Collectively, these efforts can help inform prevention strategies to avoid or mitigate future outbreaks and lead to further changes in the way food is grown and processed, which could make leafy greens safer for the public to consume.”