In the summer of 2011, 8 states reported 24 cases of Salmonella Muenchen infections associated with consuming iceberg lettuce. Illness onset dates ranged from June 27 through August 12. Six people of 11 cases in Minnesota were hospitalized. No one died.

The Minnesota Department of Health (MDH) conducted a case-case comparison study, 29 non-Muenchen Salmonella and E. coli O157:H7 cases with illness onsets from June 1 through July 15, 2011 were used as a comparison group. Consumption of iceberg lettuce (8 of 9 S. Muenchen cases vs. 10 of 28 comparison cases; odds ratio [OR], 14.4; 95% confidence interval [CI], 1.6 to 132.3; p = 0.008) and consumption of cabbage (5 of 9 S. Muenchen cases vs. 4 of 29 comparison cases; OR, 7.8; 95% CI, 1.4 to 42.1; p = 0.02) were associated with illness.

Minnesota Department of Agriculture initiated traceback investigations of the iceberg lettuce consumed at restaurants by eight Minnesota cases. Six different distributors were identified from point of service records, but it was not clear from the invoices what types of lettuce were received (e.g., iceberg vs. other, shredded vs. whole head). Further analysis of upstream distribution was not pursued.