2020 E. coli Outbreak Linked to Unknown Source 3 – Investigation Updates

November 10, 2020

CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are investigating a multistate outbreak of E. coli O157:H7 infections.

Public health investigators are using the PulseNet system to identify illnesses that may be 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 were closely related genetically. This means that people in this outbreak are more likely to share a common source of infection.

As of November 9, 2020, a total of 12 people infected with the outbreak strain of E. coli O157:H7 have been reported from six 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 September 2, 2020, to October 14, 2020. Ill people range in age from 8 to 62 years, with a median age of 21 years. Sixty-seven percent of ill people are female. Of 11 ill people with information available, 5 have been hospitalized. No deaths have been reported.

Illnesses might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of E. coli O157 Infection for more details.

Investigation of the Outbreak

On November 6, 2020, Tanimura & Antle recalled packaged single head romaine lettuce after the Michigan Department of Agriculture and Rural Development (MDARD) identified E. coli O157:H7 in a sample of the packaged romaine lettuce. WGS results showed that the E. coli strain in the romaine lettuce sample was closely related genetically to the E. coli strain identified in ill people.

State and local public health officials are interviewing ill people to determine what they ate and other exposures in the week before they got sick. Of the 11 people interviewed, all reported eating various types of leafy greens, including romaine lettuce (5), spinach (5), iceberg lettuce (3), and red leaf lettuce (3).

There is not enough epidemiologic and traceback information available at this time to determine if ill people got sick from eating Tanimura & Antle romaine lettuce. The investigation is ongoing to determine if additional products may be contaminated with the outbreak strain of E. coli.

Do not eat, sell, or serve Tanimura & Antle’s recalled packaged single head romaine lettuce.

CDC will provide more information as it becomes available.