An investigation into a norovirus outbreak among patrons of an Illinois restaurant has ended after identifying 173 people who became ill.

The McHenry County Department of Health began the investigation into D.C. Cobb’s restaurant after a cluster of illnesses was linked to the business beginning in late August and running through mid-September.

Norovirus was identified as the pathogen, but the investigation could not determine exactly how it was introduced into the facility. However, five employees were found to have been ill. A complete report of the investigation is available in Communicable Diseases Data and Reports under Foodborne and Waterborne Illness Reports.

“The case-control study conducted by MCDH identified 173 ill individuals, 168 patrons who experienced vomiting and/or diarrhea after eating food from D.C. Cobb’s from Aug. 29, 2022, through Sept. 16, 2022, and five staff who experienced vomiting and/or diarrhea before or after working at D.C. Cobb’s McHenry from Aug. 29, 2022, through Sept. 19, 2022,” according to the report.

“A case-control study identifies a sample of ill individuals during a specific timeframe and does not necessarily identify all individuals who became ill. The total number of ill individuals identified via this case-control study may therefore underreport the total number of ill individuals associated with this cluster of illness.”

A food item analysis identified that people were approximately 2.2, 3.5, or 2.7 times more likely to be ill after eating salad, the southwest chicken wrap, or the fried pickles with Cobb’s southwest sauce, respectively. Three other dishes were found to be associated with illness, although they are not as strongly implicated as a cause of illness: Cobb’s nachos, dynamite shrimp, and vampire tacos with bacon. Additionally, the food item analysis identified that people were approximately 2.4 or 3.3 times more likely to be ill after eating lettuce or green onion, respectively. Taken together, the analyses for dishes and ingredients indicate multiple dishes and ingredients were associated with illness.

“Norovirus is highly infectious and is easily spread person to person and on surfaces that have not been properly cleaned and sanitized. At least five employees were confirmed, through the employee survey, to have worked at the food establishment during their infectious period after being ill with Norovirus symptoms consistent with the case definition for this outbreak. These employees returned to work within 24 hours after their symptoms subsided. Food handlers are required to be excluded from work a minimum of 48 hours after being symptomatic and must be educated about good hand hygiene,” according to the health department report.

The Division of Environmental Health identified multiple breakdowns in critical operational procedures that created an environment where norovirus could remain viable and be readily transferred from food handlers to surfaces, surfaces to food items or patrons, and food handlers to food items – all of which could result in illness spreading to patrons. The most significant of these operational deficiencies are as follows:

1. Failure to provide hot water at a minimum temperature of 100 degrees Fahrenheit at the kitchen food service hand sinks.

2. Food preparation taking place where there was no access to a food service hand sink

3. Improper hand washing procedures and washing of hands at sinks that are not designated

as food service hand sinks

4. Failure to provide paper towels at one of the food service hand sinks

5. Failure of a food handler to wear food service gloves to cover artificial fingernails

6. Failure to provide a procedure for reporting/correcting a lack of tempered water and/or

lack of soap and paper towels at a food service hand sink

7. Approximately 30 percent of employees indicated that there is no monitoring of handwashing practices by management.

8. Failure of food service employees to recognize that their responsibilities include the

handling and/or service of ready-to-eat foods. Ready-to-eat foods require additional hand

washing procedures and barriers to prevent the transfer of contaminants to food items.

9. Multiple employees indicated that handwashing takes place either in the bathroom or at a

sink that is not designated for hand washing purposes only.

10. Failure to provide information regarding handwashing at appropriate stages in the food

preparation/food handling processes during the product flow evaluations.

11. While the correct minimum internal cooking temperatures were provided by interviewed

staff, no detailed information was provided regarding who/how the internal temperature of the food product is actually verified. Prep staff appears to utilize cooking time as the primary control.

12. Soiled food contact surfaces.

13. Chemical dish machine not reaching the minimum sanitizer concentration to sanitize


14. Failure to provide test kits to ensure that sanitizer levels are at effective and safe levels.

After MCDH staff conducted an inspection and provided corrective action, D.C. Cobb’s employees and management responded quickly, reducing the transmission of illness associated with the outbreak, according to health officials.

“The management of D.C. Cobb’s fully cooperated with the illness investigation team and continues to work with Division of Environmental Health staff to implement additional strategies to prevent future public health concerns,” said Patti Nomm, MCDH’s Director of Environmental Health.

Norovirus is a highly contagious virus that spreads quickly from person to person or through contaminated items, and it cannot be treated with antibiotics. Symptoms of norovirus include diarrhea, vomiting, nausea, and stomach pain that usually last between 24 hours and 48 hours. Anyone with norovirus illness should stay home when sick and for 24 hours after experiencing vomiting or diarrhea.

Routinely cleaning and sanitizing kitchen utensils, counters and surfaces before preparing food can reduce the risk of norovirus. Good hygiene practices are equally important whether or not food is being prepared.