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A foodborne norovirus outbreak in a healthcare facility, Austria, 2009

Abstract number: P1167

Kuo H.W., Hell M., Kasper S., Lederer I., Allerberger F., Schmid D.

Objectives: A foodborne norovirus outbreak occurred in a health care facility in Austria, from March 15 to March 27, including a total of 167 cases. Six out of ten cases tested were positive for norovirus. With a maximum of 91 cases on March 17, the pattern of the outbreak spread indicated foodborne origin, followed by a person-to-person spread. The kitchen was disinfected on March 17, and it can be assumed that 114 resident-cases with disease onset from March 16 to March 18 were suspected to be foodborne. A case-cohort study was performed among the residents of the affected premises to test the hypotheses that exposure to specific food items served on March 14, 15 and 16 was associated with increased risk of norovirus infection.

Methods: Out of the cohort-at-risk, including 510 residents who were exposed to food at least on one of the three risky days (March 14, 15 and 16), 274 persons were randomly selected regardless of the disease status for the reference-group. The study subjects were interviewed by self-administered questionnaire or face-to-face interviews on their exposure to food items served on the risky days. Out of the 388 study subjects, 350 responded to the questionnaire (response rate: 90%) and therefore remained for the case-cohort analyses.

Results: The analyses revealed that consumption of a particular cold cut (sausage) served on March 15 (OR = 3.98, 95% CI: 1.18–14, p = 0.0166), a soup served with sliced bread (OR = 1.88, 95% CI: 1.11–3.18, p = 0.0176), a meat dish with rice and salad (OR = 2.03, 95% CI: 1.16–3.55, p = 0.0112), and a rolled pancake filled with spinach served on March 16 (OR = 1.72, 95% CI: 1.03–2.88, p = 0.037) were associated with increased risk of a norovirus infection (Table 1).

Conclusion: Each of these epidemiologically identified risk-associated food items could have been easily contaminated with norovirus during preparation. Out of the 26 kitchen staff-members tested, 11 were positive for norovirus. Out of these, 5 kitchen staff members – who stated to have been asymptomatic – were on duty during the weekend prior to the outbreak. Repeated training of food handlers working in health care facilities in hand hygiene and environmental disinfection, and the implementation of the concept of hazard analysis and critical control points are indispensable to prevent foodborne norovirus outbreaks in health care facilities.

Table 1. Food items associated with increased risk of norovirus infection, odds ratio (OR) and 95% confidence interval (95% CI)

Food itemsUnivariable analyses
 OR95% CIp
March 15 breakfast   
Particular cold cut (sausage)3.981.18–140.0166
March 16 lunch   
Soup served with sliced bread1.881.11–3.180.0176
Meat dish with rice and salad2.031.16–3.550.0112
March 16 dinner   
Rolled pancake filled with spinach1.721.03–2.880.037

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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