Federal health officials unable to identify source of E. Coli outbreak

Epidemiologic and traceback evidence showed that leafy greens were the likely source of a multistate outbreak of E. coli O157:H7 infections this fall, but federal health officials said they were unable to identify a specific type or brand of leafy greens responsible. 

The now-over outbreak, one of three E. coli outbreaks investigated this fall, hospitalized 20 and sickened 40 in 19 states, according to the Centers for Disease Control and Prevention. Illnesses started on dates ranging from Aug. 10 to Oct. 31, according to the CDC. 

The Food and Drug Administration and state partners conducted inspections on farms of interest and collected environmental samples. Teams were deployed to dozens of ranches in the region to conduct large-scale environmental sampling, but the CDC said no Shiga toxin-producing E. coli were found on leafy greens.

FDA said in a Dec. 22 update that it is analyzing environmental samples and continuing the agency’s investigations to identify the root cause of this outbreak.

State and local public health officials interviewed ill people to determine what they ate and other exposures in the week before they got sick. Of the 23 ill people interviewed, 22 reported eating or maybe eating a variety of leafy greens, including spinach (16) and romaine lettuce (15). 
FDA said it completed traceback investigations for several types of leafy greens ill people reported eating. Several farms of interest were identified, but no single ranch was a common source of the leafy greens. 
The FDA and CDC were unable to identify a particular food source of the two other E. coli outbreaks this fall.

Still waiting

“I’m thankful that FDA and CDC noted that the outbreaks are over, and provided an update on the status of the investigations,” Jennifer McEntire, senior vice president of food safety and technology for the United Fresh Produce Association, said in an e-mail. “It is, of course, discouraging to be left wondering, yet again, what caused these outbreaks to occur.”

McEntire said she was hopeful that the longitudinal studies underway in Arizona and beginning in California, combined with the application of whole genome sequencing some historical isolates, will shed new light on the hazards in the environment.

“FDA is also taking a hard look at how tracebacks and outbreak investigations are done,” she said. “I expect there will be a report on this evaluation, and ideally some recommendations to improve the partnership between the agency and the industry that is needed to facilitate collaboration during outbreaks.”

The Produce Marketing Association issued a statement to its members and the media about the update from the agencies. PMA noted that, since the beginning of the outbreak, CDC and FDA have not recommended that consumers avoid any product.

“The industry has invested significantly into traceability to facilitate removal of tainted product from commerce,” PMA said in the statement. 
“PMA continues to convene experts to identify production practices that have a realistic chance of reducing the risk of contamination and transfer. The risk will never be zero, but we continue to monitor emerging science-based knowledge and support the leafy greens supply chain as they strive to reduce the risk of foodborne illness. If we are to get close to that goal, it will require sharing of data and a meaningful collaboration of the partners in the industry, academia and government. It will also require a systems approach and continued investment into food safety research.”