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Volume 17, Number 3—March 2011

Research

An Integrated Approach to Identifying International Foodborne Norovirus Outbreaks1

Linda VerhoefComments to Author , Roger D. Kouyos, Harry Vennema, Annelies Kroneman, Joukje Siebenga, Wilfrid van Pelt, Marion P. Koopmans, and on behalf of the Foodborne Viruses in Europe Network
Author affiliations: Author affiliations: National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands (L. Verhoef, H. Vennema, A. Kroneman, J. Siebenga, W. van Pelt, M. Koopmans); Swiss Federal Institution of Technology (ETH) Zurich, Switzerland (R. Kouyos)

Main Article

Table A1

Summary of aggregated data of clustered outbreak strains, sequences, and properties of the outbreaks within such clusters for each of the genotypes, 1999–2008.*

GT Total no. strains No. (%) strains
in clusters No. (%) strains not in clusters Minimum similarity within GT, % Total no.
clusters Cluster size,
range† Cluster size, median† No. (%) FB outbreak strains No. sign
possible
FB clusters No. (%) FHB outbreak strains No. sign FHB clusters No. (%) PB outbreak strains No. sign PB clusters No. (%) UN outbreak strains No. sign UN clusters
I.1 24 19 (79) 5 (21) 91.2 4 2–7 5 8 (33)‡ 0 0 2 (8) 0 14 (58) 0
I.2 34 20 (59) 14 (41) 97.5 5 2–6 5 5 (15) 0 0 0 0 29 (85)§ 0
I.3 43 16 (37) 27 (63) 78.3 5 2–6 4 6 (14) 0 0 2 (5) 0 35 (81) 0
I.4 40 23 (58) 17 (42) 94.8 8 2–5 2 8 (20)‡ 2 (5)‡ 0 0 30 (75) 0
I.5 6 5 (83) 1 (17) 93.1 2 2–3 2.5 2 (33)§ 0 0 0 0 0 4 (67) 0
I.6 20 13 (65) 7 (35) 88.7 4 2–5 3 4 (20)§ 1# 1 (5)§ 0 2 (10) 0 13 (65) 0
II.1** 28 10 (36) 18 (64) 90.9 4 2–3 2.5 6 (21)‡ 0 0 0 12 (43)‡ 0 10 (36) 0
II.2 30 9 (29) 21 (71) 82.4 4 2–3 2 11 (37)‡ 0 0 0 3 (10) 0 16 (53) 0
II.3** 136 70 (52) 66 (48) 90.5 14 2–15 3 15 (11) 0 0 0 35 (26)‡ 4¶# 86 (63) 0
II.4** 950 691 (73) 254 (27) 82.4 47 2–361 3 41 (4) 3¶# 2†† 0 178 (19)§ 3¶# 729 (77)‡ 4¶#
II.5 3 2 (66) 1 (33) 97.0 1 2 2 1 (33) 0 0 0 0 (0) 0 2 (67) 0
II.6** 54 30 (56) 24 (44) 92.0 8 2–15 2 11 (20)‡ 1 (2) 0 6 (11) 36 (67) 0
II.7 57 39 (68) 18 (32) 96.2 4 2–28 3 13 (23)‡ 1# 0 0 6 (11) 38 (67) 0
II.8 4 2 (50) 2 (50) 96.0 1 2 2 2 (50)‡ 0 0 0 0 (0) 0 2 (50) 0
II.10 3 0 3 (100) 97.0 0 NA NA 0 0 0 0 2 (67)§ 0 1 (33) 0
II.11 1 0 1 (100) NA 0 NA NA 0 0 0 0 0 0 1 (100) 0
II.12 4 0 4 (100) 93.9 0 NA NA 0 0 0 0 0 0 4 (100) 0
II.13 3 0 3 (100) 96.6 0 NA NA 1 (33) 0 0 0 0 0 2 (67) 0
II.14 3 0 3 (100) 99.5 0 NA NA 1 (33) 0 0 0 0 0 2 (67) 0
II.16 4 0 4 (100) 97.5 0 NA NA 0 0 0 0 1 (25) 0 3 (75) 0
II.17 1 0 1 (100) NA 0 NA NA 0 0 0 0 0 0 1 (100) 0
II.NA1 6 2 (50) 4 (50) 94.2 1 2 2 0 0 0 0 2 (50) 0 2 (50) 0
II.NA3
1
0
1 (100)
NA
0
NA
NA
0
0
0
0
0
0
1 (100)
0
Overall 1456 938 (64) 518 (36) 112 2–364 136 (9) 10 6†† 1 252 (17) 9 1062 (73) 4

*GT, genotype; FB, foodborne; FHB, food-handler borne; PB, person-borne; UN, unknown; NA, not applicable.
†Size of a strain cluster is the number of outbreak-representative strains within a molecular cluster of outbreaks, i.e., 2–7 outbreaks (not 2–7 patients per outbreak)
‡Genotypes with significantly higher proportion (p<0.05) of outbreaks with this transmission mode, when compared to the proportion in the total sequence population.
§Genotypes with borderline significantly higher proportion (0.05<p <0.10) of outbreaks with this transmission mode, when compared to the proportion in the total sequence population.
¶Clusters with significantly higher proportion (p < 0.05) of outbreaks with this transmission mode, when compared to the proportion within the genotype.
#Clusters with borderline significantly higher proportion (0.05<p<0.10) of outbreaks with this transmission mode, when compared to the proportion within the genotype.
**Genotypes II.1, II.3, II.4 and II.6 were aligned separately for different genomic regions.
††Percentage values <0.5.

Main Article

1Some of these data were presented as a poster during the 15th International Bioinformatics Workshop on Virus Evolution and Molecular Epidemiology, September 7–11, 2009, Rotterdam, the Netherlands.

2Members of the Foodborne Viruses in Europe Network who contributed to this study are listed at the end of this article.

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