In July 2021 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 O121 infections linked to cake mix.

Sixteen people infected with the outbreak strain of E. coli O121 were reported from 12 states. Illnesses started on dates ranging from February 26, 2021 to June 21, 2021.

Sick people range in age from 2 to 73 years, with a median age of 13, and 100% were female. Of 16 people with information available, 7 were hospitalized. One person developed a type of kidney failure called hemolytic uremic syndrome (HUS), and no deaths were reported.

The U.S. Food and Drug Administration (FDA) conducted a traceback investigation using purchase records from locations where sick people bought cake mix but did not determine the source of the outbreak.

Whole genome sequencing of bacteria from six people’s samples predicted resistance to sulfisoxazole, streptomycin, and trimethoprim-sulfamethoxazole for one sample and did not predict any resistance for five samples. Standard antibiotic susceptibility testing by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory . These findings do not affect treatment guidance since antibiotics are not recommended for patients with E. coli O121 infections.

The outbreak was declared over on September 16, 2021.