Volume 15, Number 1—January 2009
Research
Selection Tool for Foodborne Norovirus Outbreaks
, Annelies Kroneman, Yvonne van Duynhoven, Hendriek Boshuizen, Wilfrid van Pelt, Marion Koopmans, on behalf of the Foodborne Viruses in Europe Network
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.
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).