Possible Foodborne Illness Outbreak
Indiana Epidemiology Newsletter
Mona Wenger, MS
Field Epidemiologist District 2
On December 13, 2006, the Elkhart County Health Department (ECHD) notified the Indiana State Department of Health (ISDH) of a possible foodborne illness outbreak associated with a local food establishment. Predominant symptoms included nausea, vomiting, and diarrhea.
The ECHD and the ISDH initiated a collaborative investigation of the outbreak. Two questionnaires were used in the investigation. The ECHD used an environmental health food establishment questionnaire to assess food preparation practices and employee illness. The ISDH used an enteric questionnaire to determine patron illness onset, symptoms, and food consumption. Seventeen patrons and three employees were interviewed during the investigation. A case was defined as any individual who consumed a meal at the food establishment or was epidemiologically linked to a patron who had consumed a meal at the food establishment and developed vomiting or diarrhea on or after December 10, 2006. Fourteen individuals met the case definition (Figure 1). The mean duration of illness was 37 hours (range: 1 to 144 hours). The incubation period ranged from 28 to 58 hours. One individual was hospitalized. Three symptomatic patrons submitted stool specimens for bacteriologic and viral testing at the ISDH Laboratories.
Figure 1: Elkhart County's Norovirus Outbreak with Number of Cases and Illness Onset Dates
On December 13, 2006, a representative of the ECHD visited the food establishment to review food-preparation practices, including Hazard Analysis of Critical Control Points, and to inquire about employee illness. No food samples were collected, because no common food item had been identified as the suspected vehicle.
The investigation revealed that some food-holding temperatures were below the required 135° F minimum. The employee at the front cash register was not using gloves or utensils for dispensing ice or lemon slices into patrons’ beverages and frequently touched her face and clothing without washing her hands. Patrons’ trays were not sanitized after each use. The manager revealed that three food handlers had been ill with runny nose, sore throat, nausea, vomiting, and diarrhea prior to the patrons becoming ill.
Three stool specimens were analyzed for bacteriologic (E. coli 0157: H7, Campylobacter, Shigella, and Salmonella) and viral (Norovirus) pathogens at the ISDH Laboratories. All three samples tested positive for Norovirus andnegative for bacteriologic pathogens.
The investigation confirmed that an outbreak of gastroenteritis among patrons and staff of an Elkhart County restaurant occurred from December 10-14, 2006. Although no specific food item was identified as a vehicle of illness, the only common exposure reported was consumption of a meal at the food establishment on December 10, 2006.
The causative agent of this outbreak was Norovirus. Three patrons tested positive. In addition, nine other patrons and two employees had symptoms compatible with Norovirus infection from December 10-14. Two secondary cases were also identified among the groups of patrons.
Norovirus is found in the vomit or stool of infected people. Common transmission routes include consumption of contaminated foods or liquids, contact with contaminated surfaces or objects, and contact with someone who is infected. The virus is highly contagious and environmentally stable. The incubation period is 24-48 hours. Symptoms of Norovirus infection include nausea, vomiting, diarrhea, and some stomach cramping. Symptoms may also include a low-grade fever, chills, headache and body aches, and fatigue. The illness often begins suddenly and lasts 24-48 hours, with most individuals resolving without complications. Infected people can shed the virus for as long as two weeks after recovery.
Foodborne outbreaks of viral gastroenteritis usually occur when an infected food handler with inadequately washed hands prepares food that is served raw (e.g., salads, vegetables, etc.) or that is handled extensively after cooking (e.g., sliced sandwich meats, rolls, etc.). Two employees who met case definition experienced illness onset prior to the outbreak. The food establishment in question served several ready-to-eat food items. To minimize the risk of further transmission, the establishment sanitized all contact surfaces with a 1:10 bleach-water solution, including patrons’ trays, and educated employees on proper hand washing.
In general, most Norovirus outbreaks can be prevented by strictly adhering to the following guidelines:
1) Thoroughly wash hands with soap and water before, during, and after preparing and serving food; after using the restroom; and after assisting someone who has diarrhea and/or vomiting.
2) Persons with diarrhea and/or vomiting should not prepare food for others and should limit direct contact with others as much as possible.
3) Children ill with diarrhea and/or vomiting should not attend daycare or school.
4) Persons with diarrhea and/or vomiting or Norovirus infection shall be excluded from employment involving food handling1.
The Indiana State Department of Health extends its appreciation to the Elkhart County Health Department and the restaurant staff for their cooperation and participation in this investigation.
1. Indiana Retail Food Establishment Sanitation Requirements, 410 IAC 7-24-122.
More information on norovirus can be found at: http://www.in.gov/isdh/25448.htm