gms | German Medical Science

50. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie (gmds)
12. Jahrestagung der Deutschen Arbeitsgemeinschaft für Epidemiologie (dae)

Deutsche Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie
Deutsche Arbeitsgemeinschaft für Epidemiologie

12. bis 15.09.2005, Freiburg im Breisgau

Bakery products as vehicles for Hepatitis A transmission: An outbreak investigation in North Rhine-Westfalia and Rhine Land-Palatine, April 2004

Meeting Abstract

  • Karl Schenkel - Robert Koch-Institut, Department for Infectious Diseases Epidemiology, Berlin
  • Christoph Grabe - Local Health Department, Siegen
  • Horst Baumeister - Institute of Public Health, North Rhine- Westfalia
  • Marina Höhne - Robert Koch-Institut, Department for Epidemiology of Viral Infections, Berlin
  • Viviane Bremer - Robert Koch-Institut, Department for Infectious Diseases Epidemiology, Berlin
  • Andrea Ammon - Robert Koch-Institut, Department for Infectious Diseases Epidemiology, Berlin
  • Katharina Alpers - Robert Koch-Institut, Department for Infectious Diseases Epidemiology, Berlin

Deutsche Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie. Deutsche Arbeitsgemeinschaft für Epidemiologie. 50. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie (gmds), 12. Jahrestagung der Deutschen Arbeitsgemeinschaft für Epidemiologie. Freiburg im Breisgau, 12.-15.09.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05gmds328

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Veröffentlicht: 8. September 2005

© 2005 Schenkel et al.
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By April, 6th 2004, 28 cases of hepatitis A (HA) had been notified to the local health authorities in two districts in southern North Rhine-Westphalia. In comparison, in the preceding years, on average eleven cases/year had been notified in both districts combined. An investigation was initiated by the department of infectious disease epidemiology at the Robert Koch-Institute in cooperation with the local and the regional health authorities to identify the source of infection.


Cases of hepatitis A were retrieved from notification records of six involved district health offices and described by time, place and person. Early exploratory interviews suggested the hypothesis that HAV cases had consumed bakery-products of company X, where two employees had been diagnosed with HA in February.

In order to identify the vehicle of transmission, a case-control study investigating the consumption of various products of company X during the most likely incubation period was initiated among persons older than 16 years. Cases were defined as residents of six districts adjacent to Company X with jaundice, fever, abdominal discomfort or elevated serum aminotransferase levels with disease onset 1 March to 8 April and with a positive serology for Anti-HAV-IgM-antibodies. Two controls per case were randomly selected by random digit dialling. Serum samples from cases were tested for HAV RNA by PCR and the VP1 region was sequenced. An inspection of company X was performed.


Sixty-four cases with disease onset between March, 1st and April, 8th, 2004 were identified. The residences of all cases followed a distribution pattern of the bakery stores of local food company X. Two infected family members (father and son) had been working in the bakery production line of company X before falling ill with hepatitis A on February 5th and 27th, retrospectively. The father developed clinical disease 18 days after a contact vaccination for Hepatitis A.

Thirty-four (53.1%) of the cases were male, the median age was 40.5 years. Fifty-two cases and 112 controls equalling or older than 16 years were eligible for the case-control study. Forty-six of 52 (88.5%) cases and 37/112 (33.0%) controls had consumed products of company X (OR 15.5, 95% CI 6.1-39.7).

Among those who had bought food at company X, 36/46 (78.3%) cases and 16/37 (43.2%) controls had consumed pastries (OR 4.7, 95% CI 1.8-12.3).

25/46 (54.3%) cases and 12/37 (32.4%) controls had consumed filled donuts (OR 2.5, 95% CI 1.0-6.1).

After adjusting for age and sex in a logistic regression, consumption of company X filled doughnuts remained positively associated with disease (OR 3.6, 95% CI 1.3-9.8).

HAV-RNA was found in 22/27 (81.5%) IgM-positive cases and one of the employees at company X. Sequence analysis indicated 100% homology between strains of cases and this employee.


The distribution of cases over time suggested a common source of infection.

Results from our case-control study and environmental inspections suggest that company X filled doughnuts were the vehicle of this outbreak. We considered a contamination of the bakery products by the second infected employee of company X between 18 and 27 February as most probable, supported by the results from sequence analysis and descriptive epidemiology.

Our findings underline the increasing possibility of HA outbreaks due to the continuing decline in naturally acquired immunity in the population in Germany. Since 1967, only very few Hepatitis A outbreaks due to consumption of bakery products have been reported [1], [2], [3], [4]. Most of them were based on epidemiological evidence only. In the current investigation, the results of a case-control study went in concordance with the results of descriptive epidemiology, strain sequencing and environmental inspections. However, recall bias due to the long incubation time and rumours about company X (starting to spread when the case-control study began) cannot be excluded. More information about Hepatitis A background strain circulation in Germany might be useful in order to improve evidence drawn from molecular typing.

Our conclusions from this outbreak were to advise company X employees to be actively vaccinated for HA when sero-negative and to strictly observe and evaluate hygiene precautions such as hand washing and skin disinfection.

Finally, we recommended considering a prolongation of the compulsory work absence for food handlers after HA contact vaccination for up to 3 weeks or longer.


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