January 15, 2020

CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administrationexternal icon investigated a multistate outbreak of Shiga toxin-producing E. coli O157:H7 infections. This investigation included illnesses in Canada reported by the Public Health Agency of Canadaexternal icon. This outbreak was caused by a different strain of E. coli O157:H7 than the outbreak linked to romaine lettuce from the Salinas, California, growing region.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting is performed on E. coli bacteria isolated from ill people by using a standardized laboratory and data analysis method called whole genome sequencing (WGS). CDC PulseNet manages a national database of these sequences that are used to identify possible outbreaks. WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people in the United States and Canada were closely related genetically. This means that people in this outbreak were more likely to share a common source of infection.

A total of 10 people infected with the outbreak strain of E. coli O157:H7 were reported from five states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.

Illnesses started on dates ranging from November 5, 2019, to November 16, 2019. Ill people ranged in age from 21 to 91, with a median age of 33. Among ill people, 60% were female. Four of ten ill people were hospitalized, including one person who developed hemolytic uremic syndrome, a type of kidney failure. No deaths were reported.

WGS analysis of isolates from 10 ill people identified antibiotic resistance to chloramphenicol, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. Standard antibiotic resistance testing of clinical isolates by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is currently underway. These findings do not affect treatment guidance since antibiotics are not recommended for patients with E. coli O157 infections.

Investigation of the Outbreak

Information collected during the investigation indicated that Fresh Express Sunflower Crisp chopped salad kits were the likely source of this outbreak.

State and local public health officials interviewed ill people to determine what they ate and other exposures in the week before their illness started. Of 10 ill people with information available, all 10 (100%) reported eating any leafy greens in the week before their illness started. Eight ill people specifically reported eating or maybe eating a Fresh Express Sunflower Crisp chopped salad kit.

Romaine lettuce was one of the ingredients in the salad kit, but the investigation was not able to determine if romaine lettuce was the contaminated ingredient in the salad kit. For more information about the traceback investigation, visit the FDA websiteexternal icon.

As of January 15, 2020, this outbreak appears to be over.