CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) investigated a multistate outbreak of E. coli O157:H7 infections. A total of 19 outbreak associated cases were reported by 9 states. Six people were hospitalized. No one died. Illness onset dates ranged from September 2, 2020 to November 6, 2020.

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 13 people interviewed, all reported eating or maybe eating various types of leafy greens, including romaine lettuce (9), spinach (9), and iceberg lettuce (7).

Laboratory testing identified the outbreak strain in a sample of Tanimura & Antle romaine lettuce in a single-head package, which was recalled on November 6, 2020. However, investigators were unable to determine if any ill people in this outbreak got sick from eating the recalled product. No one specifically reported eating Tanimura & Antle romaine lettuce, and some people got sick before the “packed on” dates for the recalled products.

FDA conducted traceback investigations and worked with state partners to conduct inspections at several farms. However, none of the findings identified a common source in the distribution chain or linked the farms to the outbreak.

As of December 18, 2020, the outbreak declared over. This outbreak ended before enough information was available for investigators to identify the likely source.