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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 Koopmans, 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 A2

Characteristics of 29 strain sequence clusters with identical capsid sequences that may share a common exposure through food, 1999–2008*

Cluster No. strains (% total in GT) Minimum no. NT overlap Transmission mode based
on reports† (p value) Source category Time span Countries involved Reported to FBVE as linked outbreak
Selection criterion 1: identical clusters within FB genotypes including at least 1 FB outbreak, n = 22
1 (I.1) 7 (29) 204 UN? (0.38) Shellfish 2004 Sep–Dec and Feb 2006 FR, HU, GB Yes, in FR
2 (I.1) 4 (17) 204 FB (0.01) Shellfish 2000 Apr–Nov and 2001 FR, NL Yes, in FR
3 (I.1) 2 (8) 206 FB? (0.11) Unknown 2000 FR No
4 (I.1) 6 (25) 221 UN? (0.20) Unknown 2000 Dec–2005 Dec and 2006 FR, GB, SE No
5 (I.4) 5 (13) 204 FB? (0.45) Water, berries 2000 and 2002 Feb–2006 Aug NL, FR, SE No
6 (I.4) 2 (5) 204 FB (0.04) Shellfish 2000 and 2001 NL No
7 (I.4) 2 (5) 215 FHB (0.00) RTE Mar 2006 DK Yes
8 (I.5) 3 (50) 204 FB? (0.25) Shellfish, delicatessen 2004 Nov–2006 Feb IE, FR No
9 (I.6) 5 (25) 204 FB (0.07) Self-served meal, shellfish 2002 Dec–2006 Jul HU, NL, SE No
10 (I.6) 3 (13) 291 FHB? (0.14) Self-served meal 2002 Sep and 2004 SE No
11 (II.1) 3 (11) 272 FB? (0.11) Water 2000 Sep–2001 Jan FR No
12 (II.1) 3 (11) 268 FB?(0.29) Unknown 2001 Jan–Mar NL No
13 (II.2) 2 (6) 255 FB? (0.14) Shellfish 2006 Dec and 2007 Mar FR No
14 (II.2) 2 (6) 235 FB? (0.60) Shellfish 2005 Jan and 2008 Feb FR, GB No
15 (II.2) 2 (6) 338 FB? (0.60) Water 2002 Oct and 2003 Mar SE No
16 (II.6) 2 (4) 255 FB (0.04) Paella 2007 Sep FR Yes
17 (II.6) 15 (28) 45 PTP? (0.22) Berries, RTE 2004 Jan–2006 Dec HU, SE, DK, GB, FR, NL, IT Yes, multiple countries and genotypes
18 (II.6) 2 (4) 196 FB? (0.36) Self-served meal 2006 Jan–May GB, NL No
19 (II.7) 28 (49) 94 UN?(0.55) Self-served meal, RTE 2003 Jun–2006 Apr GB, DK, NL, FR, SE No
20 (II.7) 2 (4) 337 FB (0.05) RTE 2004 Feb SE No
21 (II.7) 5 (9) 249 PTP (0.01) RTE 2005 Dec–2006 Mar SE No
22 (II.8)
 2 (50)
 338
 FB? (0.25)
 berries
 2006 Jun and Aug
 SE, PL
 Yes, multiple genotypes, link abroad
Selection criterion 2: identical clusters significantly associated with FB transmission, n = 5
23 (I.2) 2 (6) 206 FB (0.02) Unknown 2000 Apr FR No
24 (I.3) 2 (5) 206 FB (0.02) Shellfish 2000 Apr FR No
25 (II.4) 35 (4) 140 FB (0.05) RTE, shellfish, berries 2006 Jan–2006 Nov FR, DK, SL, IE, HU, SE, IT, NL Yes, local link hospitals
26 (II.4) 2 (0) 238 FB (0.08) Unknown 2008 Feb FR Yes
27 (II.4)
 2 (0)
 249
 FB (0.08)
 Unknown
 2000 Nov and 2001 Dec
 NL
 No
Selection criterion 3: identical clusters statistically associated with a specific food class (shellfish, berries, water, other), n = 2
28 (I.3) 4 (9) 234 FB? (0.45) Water, berries 2000 and 2002 Feb–2006 Aug FR, DE, SE No
29 (II.4) 12 (1) 227 UN? (0.20) Shellfish 2007 Oct–2009 Nov FR, IE No

*Outbreak clusters were selected based on one of 3 criteria: 2a) genotype preferentially found in food-borne outbreaks; 2b) food-borne mode of transmission more commonly reported for cluster and 2c) specific food item more commonly reported in given cluster of outbreaks. Outbreak clusters in boldface were international outbreaks newly identified through the analysis in this study, other international outbreak clusters had already been reported as (suspected) common source events. FBVE, Food-Borne Viruses in Europe; GT, genotype; UN, unknown; FR, France; HU, Hungary; GB, Great Britain; FB, foodborne; NL, Netherlands; SE, Sweden; FHB, foodhandler-borne; RTE, ready-to-eat; DK, Denmark; IE, Ireland; PTP, person-to-person; IT, Italy; PL, Poland.
†Frequency of transmission modes as reported for the single outbreaks within the specific cluster were considered a random draw from the frequencies of this transmission mode from the background population in the Food-borne Viruses in Europe database, i.e., as random draws from a binomial distribution. p values <0.10 were considered significant or borderline significant. p values >0.10 were considered nonsignificant. However, for clusters with none of the transmission modes ending up with a significant p value, the transmission mode with the smallest p value was chosen and presented with a question mark (?).

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.

Page created: July 25, 2011
Page updated: July 25, 2011
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