Between November 1, 2010 and February 9, 2011, a total of 140 individuals from 26 states and the District of Columbia became infected with the outbreak strain Salmonella serotype I 4,[5],12:i:-. In order to ascertain the number of people connected to the outbreak, investigators performed DNA analysis of Salmonella bacteria obtained through diagnostic testing to identify cases of illness that may be part of this outbreak.

The number of ill persons identified in each state and the District of Columbia with the outbreak strain is as follows: Arkansas (1), California (1), Colorado (1), Connecticut (1), District of Columbia (1), Georgia (1), Hawaii (1), Iowa (1), Illinois (70), Indiana (13), Kentucky (1), Louisiana (1), Massachusetts (2), Maryland (1), Missouri (23), Nebraska (1), Nevada (1), New Jersey (1), New York (2), North Carolina (1), Oregon (1), Pennsylvania (4), South Carolina (1), South Dakota (1), Tennessee (2), Virginia (2), and Wisconsin (4). Among the 138 persons for whom information was available from state health departments, the Centers for Disease Control and Prevention (CDC) reported that illness onset dates ranged from November 1, 2010 to January 18, 2011.

The CDC, the Food and Drug Administration (FDA), and public health officials in many states conducted a collaborative investigation of the multi-state outbreak of Salmonella serotype I 4,[5],12:i:- infections. Half of the Salmonella infections reported occurred in Illinois, where many of the ill individuals were found to have eaten sandwiches containing sprouts at various Jimmy John’s restaurants. This prompted FDA and the Illinois Department of Public Health (IDPH) to conduct an inspection of Tiny Greens Organic Farm, a supplier of sprouts for Jimmy John’s restaurant outlets.

During the investigation, FDA collected both product and environmental samples from Tiny Greens Organic Farm of Urbana, Illinois. One environmental (water run-off) sample yielded Salmonella serotype I 4,[5],12:i:- that was indistinguishable from the outbreak strain by Pulsed Field Gel Electrophoresis (PFGE). The results of the investigation indicated a link to eating Tiny Greens Alfalfa Sprouts or Spicy Sprouts (which contain alfalfa sprouts mixed with radish and clover sprouts) at Jimmy John’s restaurant outlets.