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Volume 15, Number 1—January 2009

Research

Selection Tool for Foodborne Norovirus Outbreaks

Linda VerhoefComments to Author , Annelies Kroneman, Yvonne van Duynhoven, Hendriek Boshuizen, Wilfrid van Pelt, Marion Koopmans, and on behalf of the Foodborne Viruses in Europe Network
Author affiliations: National Institute for Public Health and the Environment, Bilthoven, the Netherlands

Main Article

Table 2

Factors (8 of 17) of borderline significance during univariate logistic regression in a random selection of 50% of the dataset for comparison of foodborne outbreaks (group 1) and outbreaks from other modes of transmission (group 2)*

Indicator Category/measure Group 1 (n = 112) Group 2 (n = 327) Univariate,
OR (95% CI) Univariate adjusted for country, OR (95% CI) Multivariate adjusted for country, OR (95% CI)
1 General 105 325 Reference Reference Reference
Household 7 2 10.8 (2.2–52.9) 10.1 (1.6–64.3) 0.1 (0.0–1.0)
2 No. cases† 1.1 (1.0–1.1) 1.0 (0.9–1.1) 1.1 (1.0–1.2)
7 Residence 7 2 Reference Reference Reference
Restaurant‡ 36 1 10.3 (0.8–129.4) 13.2 (0.7–234.0) >999†
Healthcare institute 27 267 0.0 (0.0–0.1) 0.0 (0.0–0.1) 0.0 (0.0–0.0)
Daycare 2 15 0.0 (0.0–0.3) 0.1 (0.0–0.9) 0.0 (0.0–0.1)
Hotel/guest house 9 12 0.2 (0.0–1.3) 0.1 (0.0–1.3) 0.0 (0.0–0.1)
School 11 9 0.3 (0.1–2.1) 0.3 (0.0–2.7) 0.0 (0.0–0.2)
Other 20 21 0.3 (0.1–1.5) 0.3 (0.0–2.1) 0.0 (0.0–0.2)
17 Non-GGII.4 55 48 Reference Reference Reference
Genogroup II.4 57 278 0.2 (0.1–0.3) 0.2 (0.1–0.4) 0.4 (0.2–1.0)
18 Attack rate* 14.0 (3.6–54.0) 6.7 (1.5–34.3)
19 May–Sep 20 35 Reference Reference
Oct–Apr 47 208 0.4 (0.2–0.7) 0.5 (0.3–1.2)
20 Duration in hours* 0.9 (0.8–0.9) 0.9 (0.8–1.0)
21 No point source 60 242 Reference Reference
Point source 43 3 58.8 (17.3–192.7) 44.7 (11.8–167.7)

*Significant factors were included in multivariate analyses to construct the final model. –, entered as a continuous variable. Parameters in italics could not be included in multivariate analysis because of missing values. OR, odds ratio; CI, confidence interval; GG, genogroup.
†A systematic retrospective check of Netherlands data showed that variables for no. of cases involved were reported to the national institute by regional health services when the outbreak was ongoing, and that these numbers were not updated when the outbreak had finished. The same situation was reported for other countries during the telephone survey.
‡The parameter restaurant was set to 0 because the variable was a linear combination of other variables as follows: Restaurant = intercept – household – health care – day care – hotel – school – other >999.

Main Article

1Persons contributing and countries represented: H. Vennema, E. Duizer (the Netherlands); D. Brown, B. Adak, J. Gray, J. Harris, M. Iturriza (United Kingdom); K.-H. von Bonsdorff, L. Maunula, M. Kuusi (Finland); B. Böttiger, K. Mølbak, G. Falkenhorst, C. Johnsen (Denmark); K.-O. Hedlund, Y. Andersson, M. Thorhagen, M. Lysén, M. Hjertqvist (Sweden); P. Pothier, E. Kohli, K. Balay, J. Kaplon, G. Belliot, S. Le Guyader (France); A. Bosch, A. Dominguez, J. Buesa, A. Sanchez Fauquier, G. Hernández-Pezzi (Spain); G. Szücs, G. Reuter, K. Krisztalovics (Hungary); M. Poljsak-Prijatelj, D. Barlic-Maganja, A. Hocevar Grom (Slovenia); F. Ruggeri, I. Di Bartolo (Italy); E. Schreier, K. Stark, J. Koch, M. Höhne (Germany); M. Lynch, B. Foley, P. McKeown, S. Coughlan (Ireland); K. Vainio, T. Bruun (Norway).

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