An infected food handler has been identified as the most likely source of an E. coli outbreak at an Illinois high school that saw 16 students sickened and two hospitalized.

A breakdown in hand washing protocol was the most likely cause of the illnesses, according to a 152-page report from the McHenry County Department of Health. An infected food handler was identified by laboratory testing of stool samples.

The outbreak at Huntley High School occurred in September this year. The county health department released its final report this week. The school district superintendent stated the health department’s report.

“This was an unfortunate situation that resulted in unintentional consequences. The well-being of our students and staff is our top priority. We will continue to partner with MCDH to do everything possible to ensure health and safety, including reinforcing safe food handling and sanitation practices in our cafeterias and adding additional layers of oversight as proactive measures at all Huntley 158 school cafeterias,” the district statement says.

A total of 1,526 students or staff of Huntley High School were interviewed either by Communicable Disease staff or via outbreak investigation questionnaires. Sixteen cases were identified. Fifteen out of 16 patients ate at the cafeteria on the same day.

The county health department clearly concluded that a food handler at the high school was responsible for the outbreak.

“The most likely mode of transmission of STEC (Shiga toxin-producing E. coli) in the HHS cafeteria was through an infected food handler. At the time of the investigation, an HHS food handler who worked at both the cold sandwich station, providing garnishes — lettuce and cheese — to the sandwiches, and at the cookie station was confirmed by (laboratory testing), to have been intermittently shedding STEC, Shiga toxin 2,” according to the health department report, which went on to say that the outbreak was likely larger than that documented.

“. . . Since most infections are self-limiting, most individuals do not seek health care and are not tested. Since it has been documented that STEC can be shed for up to 62 days, it is likely that the food handler was previously mildly ill and did not associate that illness with this outbreak investigation. Since shedding of the pathogen declines over time, it is not unexpected that a culture could not be performed.”

The county investigation found that of the 15 outbreak patients who ate at the cafeteria, all 15 ate a sandwich from the cold sandwich station and all cases with information available for lettuce ate lettuce on their sandwich.

County officials notified the Illinois Department of Health, the Food and Drug Administration, and the Centers for Disease Control and Prevention when the outbreak was declared. The state and federal officials thought the school outbreak might be part of a more significant multistate outbreak.

“The outbreak of STEC at HHS was linked to a multistate outbreak by WGS (whole genome sequencing),” according to the county report. 

“However, this does not imply that the source for the multistate outbreak, which is unidentified to date, is the same as for the outbreak at HHS. The multistate outbreak and the outbreak at HHS likely share a common source, with a student or staff member of HHS becoming ill with STEC after exposure to the source of the multistate outbreak at an external location. Once introduced into HHS, STEC was transmitted primarily through the HHS cafeteria.”

The county report states that the high school kitchen, regarding food safety measures, is in relatively good shape. Although some infractions, such as a faulty dishwasher, were found, those problems were resolved.

“The HHS kitchen cafeteria is well organized, with designated food handling responsibilities, and there is a clear culture of hand washing among the food handlers. Unfortunately, even an occasional breakdown in hand washing procedures or technique can result in the transmission of illness,” the county report says. 

“During observations of the food handling procedures at HHS, two food handlers failed to utilize a barrier to turn off the hand sink. This confirms that even in a kitchen with trained staff, where hand washing is encouraged, a breakdown in technique can occur, mainly when staff are extremely busy and distracted by multi-tasking.

“In this illness outbreak, the likeliest scenario is that the infected food handler failed to wash their hands correctly, or thoroughly enough, or frequently enough, which resulted in contamination of either surfaces (trays, utensils, food packaging, etc.) or food items at the cold sub sandwich station and cookie station. . .  Without a further cooking step after contamination, the pathogen remained viable, resulting in illness following consumption. STEC can be present for up to 16 months on surfaces without proper sanitization.”