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Indiana State Department of Health

Epidemiology Resource Center Home > Surveillance and Investigation > Surveillance and Investigation Division > Newsletters > Indiana Epidemiology Archived Newsletters > Epi_Newsletter_August_2007-OutbreakSpotlight Indiana Epidemiology Newsletter

August 2007

 

Brad Beard, BS
District 3 Field Epidemiologist

Background

On October 31, 2006, a representative from the Huntington County Health Department (HCHD) contacted the Indiana State Department of Health (ISDH) to report that a local caterer had reported several people becoming ill after eating at a wedding reception in Fort Wayne, Indiana. That same day, a representative from the Allen County Health Department (ACHD) contacted the ISDH to report that several people had developed symptoms of gastroenteritis after eating at Restaurant A in Fort Wayne.

Epidemiologic Investigation

The ISDH, HCHD, and the ACHD initiated investigations to describe the outbreaks, determine the mode of transmission, and identify potential sources. The ACHD had received phone calls from individuals from three unrelated parties who had eaten dinner at Restaurant A on October 22, October 28, and October 29, 2006, and reported becoming ill. The HCHD investigation focused on the private caterer who prepared the wedding reception dinner. However, upon interviewing wedding attendees about the wedding rehearsal dinner, the HCHD and the ACHD learned that guests became ill after attending the wedding rehearsal dinner, not the wedding reception. The rehearsal dinner was held at Restaurant A. A caller who attended a birthday party at Restaurant A on the same day as the wedding rehearsal dinner also reported becoming ill.

Since Restaurant A is located in Allen County, the ACHD obtained a menu of food items served on the days in question. The ACHD and ISDH developed a questionnaire to collect information on symptoms, onset of illness, illness duration, and foods consumed and initiated a case-control study. A confirmed case was defined as any previously healthy person who became ill within 72 hours after eating food from Restaurant A from October 22 through November 4 and had laboratory confirmation of a given pathogen or was epidemiologically linked to a confirmed case. A probable case was defined as any previously healthy person who became ill with compatible symptoms within 72 hours after eating food from Restaurant A from October 22 through November 4 and did not have laboratory evidence of infection or was epidemiologically linked to a confirmed case. A control was defined as anyone who ate at Restaurant A from October 22 through November 4 and did not become ill.

Interviews were completed on 135 patrons and restaurant staff, including residents of Ohio and Michigan, who attended the wedding and rehearsal dinners. One hundred patrons and employees met the confirmed and probable case definitions. Based on the information from the wedding rehearsal dinner and other related calls, the average incubation period was approximately 24 hours (see Figure 1), and the average duration of illness was approximately 24-48 hours. The predominant symptoms reported were nausea (85%), diarrhea (84%), and vomiting (80%). Several cases sought medical attention; one patron was hospitalized. Fourteen people submitted stool specimens to the ISDH Laboratories for analysis (see Laboratory Results).

Due to the limited number of controls identified, statistical analysis to identify a particular food vehicle associated with illness could not be performed.

Figure 1. Epidemic Curve of Illnesses Associated with Restaurant A from Oct 14-Nov 7, 2006. (Counts based on confirmed, probable, and suspect cases.)

Environmental Assessment

A representative of the ACHD visited Restaurant A on October 31, 2006, to review food preparation practices, collect available food samples, inquire about employee illnesses, and obtain clinical histories and exposure information on employees. At that time, no restaurant employees were reported as being ill. At the time of inspection, the final rinse on the dishwashing machine was not operating at proper temperature, a critical violation. The ACHD conducted an additional inspection of the facility on November 1, 2006. No critical violations were noted.

The ACHD inspected Restaurant A on November 2, 2006, and found that the final rinse on the dishwashing machine was still not operating at proper temperature. At this time, it was also noted that hot water was not available at the employee hand-washing sinks in the kitchen area, employee restrooms, or bar area. The restaurant voluntarily closed for 24 hours to correct these deficiencies. The ACHD conducted daily interviews of employees for symptoms of illness from November 2 until November 17, 2006. Several employees were reported ill prior to the outbreak (see Figure 1). Pursuant to the Indiana Retail Food Establishment Sanitation Requirements, 410 IAC 7-24-120-121, a retail food establishment must exclude employees exhibiting vomiting and/or diarrhea.

On November 3, 2006, a representative from the ACHD provided the employees with information on safe food handling and employee health during two different shifts. The dishwashing machine was operating at the proper rinse temperature, and hot water was provided at all the hand-washing sinks in the kitchen area, employee restrooms, and bar area. Three employees reported being ill in the morning and were excluded from the restaurant until symptoms resolved. In the afternoon, three additional employees reported being ill and were excluded from the restaurant. The restaurant reopened on the evening of November 3, 2006, after a follow-up inspection by ACHD.

Subsequent follow-up inspections on November 4-7 revealed mishandling of consumable ice, lack of soap at the hand-washing sink, food temperature violations, hot water not reaching proper temperature, and additional ill employees. ACHD and ISDH representatives conducted additional follow-up inspections on November 8-17. Several violations were noted, including ready-to-eat foods not being held at proper temperature, dishes being stored in the hand sinks, the dishwashing machine not operating at the proper temperature, and the improper use of single-use gloves. The wait staff was also observed handling ready-to-eat foods with bare hands. During one follow-up inspection, an employee was reportedly working while ill with shigellosis; this employee was identified during the collection of employee stool samples. This employee was subsequently excluded until follow-up testing could be completed. These follow-up inspections resulted in identifying additional education needs for employees and management to ensure food safety.

One patron provided a leftover sample of prime rib from the wedding rehearsal dinner on October 28, 2006, for testing (see Table 2). No food samples were available from the restaurant for testing.

Laboratory Results

Twenty-five individuals submitted stool specimens to the ISDH Laboratories for analysis. Seven patrons and six employees tested positive for Norovirus. All specimens were negative for Campylobacter, Salmonella, and E. coli O157:H7. One employee specimen tested positive for Shigella. That individual was subsequently treated and not considered related to this outbreak.

Several food items were submitted to the ISDH Laboratories for analysis. Several food samples were collected from the wedding reception before the investigation revealed that the reception was not associated with illness; all samples tested within normal limits (Table 1). One sample of prime rib was collected from Restaurant A; the prime rib was negative for bacterial agents (Table 2).

Table 1. Food Sample Analysis Report: Wedding Reception Caterer

Food Item Petrifilm APC* Total Coliforms E. coli
Candy (sub 1) 240 cfu/g not tested not tested
Candy (sub 2) 290 cfu/g not tested not tested
Chicken 100 cfu/g <10 cfu/g <10 cfu/g
Swiss Steak 30 cfu/g <10 cfu/g <10 cfu/g
Cake (sub 1) 16,800 cfu/g <10 cfu/g <10 cfu/g
Candy (sub 2) 2,400 cfu/g <10 cfu/g <10 cfu/g
Cake (sub 3) 4,200 cfu/g <10 cfu/g <10 cfu/g

*aerobic plate count

Table 2. Food Sample Analysis Report: Restaurant A Rehearsal Dinner

Food Item Petrifilm APC* Total Coliforms E. coli Shigella flexneri
Prime Rib 950 cfu/g <10 cfu/g <10 cfu/g not found

Conclusions

This investigation confirms that an outbreak of viral gastroenteritis associated with a local restaurant in Fort Wayne, Indiana, occurred from October 26 through November 4, 2006. The only common exposure among all the cases was eating at this restaurant. Due to the lack of controls, advanced statistical analysis could not be performed on the cases. Therefore, the point source of this outbreak could not be determined. Transmission of the virus may be due to a common food vehicle and/or person to person.

The causative agent of this outbreak was Norovirus. Norovirus has a world-wide distribution and is a major cause of gastroenteritis outbreaks. Transmission occurs by the fecal-oral route; however, aerosolized vomitus is also suspected. The incubation period ranges from 10-50 hours, averaging 24-48 hours. Symptoms usually last 24-48 hours and include nausea, vomiting, diarrhea, cramps, headache, and sometimes a mild fever, typical of what was reported in this outbreak. Norovirus is highly contagious, and those infected may continue to shed virus for up to two weeks after symptoms stop. Illness is typically self-limiting and is treatable with antibiotics. Dehydration is the most common complication associated with Norovirus infections.

Humans are the reservoir for Norovirus. Foodborne viral outbreaks usually occur when an infected food handler with inadequately washed hands prepares food that is served raw or ready-to-eat (e.g., salads, vegetables, etc.) or that is handled extensively after cooking (e.g., sliced sandwich meats, rolls, etc.). Although Norovirus does not replicate in food, only 50-100 viral particles are needed to cause infection. Norovirus is extremely environmentally stable and can survive freezing, temperatures up to 140°F, and chlorine concentrations up to 10 parts per million.

The investigation revealed that employees were ill prior to the outbreak and were the most likely source of infection. According to the ISDH Public Health Emergency Surveillance System (PHESS), hospital emergency department chief complaint data indicated that gastrointestinal symptoms, compatible with Norovirus infection, were prevalent in the community prior to the outbreak. The outbreak peaked on October 31. The facility was closed on November 2, and control measures were implemented. The epidemiologic curve shows the effectiveness of the control measures, particularly the exclusion of ill employees. The ISDH commends the Allen

Recommendations

In general, most viral foodborne outbreaks can be prevented by strictly adhering to the following food safety practices:

  1. Thoroughly wash hands with soap and water before and after preparing food, after using the restroom, and before eating.

  2. Always use gloves and utensils when handling ready-to-eat foods.

  3. Wash all raw fruits and vegetables prior to serving.

  4. Thoroughly cook all raw meats, seafood, and shellfish before consumption.

  5. Those ill with diarrhea and vomiting should avoid contact with others.

  6. Exclude ill food handlers until symptoms cease.

  7. Ill children and infants in diapers should be excluded from food preparation and serving areas.

  8. Any environmental surface suspected of contamination should be promptly cleaned and disinfected with bleach solution and then rinsed.

References

American Academy of Pediatrics. Caliciviruses. In: Pickering LK, ed.Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003 226.

American Public Health Association. Epidemic Viral Gastroenteropathy. In: Chin J, ed.Control of Communicable Diseases Manual 17th ed. Washington, DC: American Public Health Association; 2000, 218.

Centers for Disease Control and Prevention. Epi-Info software version 3.3.2. February 9, 2005.