14 December 2006
Increase in norovirus activity reported in Europe
A Kroneman1 (firstname.lastname@example.org), H Vennema1, J Harris2, G Reuter3, C-H von Bonsdorff4, K-O Hedlund5, K Vainio6, V Jackson7, P Pothier8, J Koch9, E Schreier9, B Böttiger10, M Koopmans1 on behalf of the “Food-borne viruses in Europe” network
1National Institute for Public Health and the Environment, Bilthoven, the Netherlands
2Health Protection Agency, Centre for Infections, London, United Kingdom
3Regional Laboratory of Virology, National Reference Laboratory of Gastroenteric Viruses, Pécs, Hungary
4Helsinki University Central Hospital, Virology Division, Helsinki, Finland
5Swedish Institute for Infectious Disease Control, Department of Virology, Karolinska Institute, Stockholm, Sweden
6Norwegian Institute of Public Health, Division of Infectious Disease Control, Oslo, Norway
7Health Protection Surveillance Centre, Dublin, Ireland
8University of Dijon, Laboratoire de Virologie, Dijon, France
9Robert Koch Institute, Berlin, Germany
10Department of Virology, Statens Serum Institut, Copenhagen, Denmark
A large increase in norovirus outbreaks in Hungary and
Germany was reported to European national health authorities via the Foodborne
Viruses in Europe network (FBVE, http://www.eufoodborneviruses.co.uk/DIVINEVENT/DIVIndex.asp
on 24 November and 4 December respectively. Subsequently, an email was sent
to all FBVE members requesting a current overview on norovirus outbreaks in
their country, and asking for preliminary reports on genotyping.
Thirteen country authorities participate in the FBVE network. Nine of
the 11 country authorities which replied to the survey indicated an increase
in norovirus activity (outbreaks and/or case reports) in October and/or
November 2006 compared with the same period in 2004 and 2005 (Table). In
two countries (France and Spain), no increase in norovirus activity was
found. Unusually high norovirus activity already in summer 2006 was reported
by the Hungarian authorities (thought to be due to a drinking-water related
outbreak) as well as the Netherlands, Denmark, Ireland, Finland and Norway.
Table. Reports of norovirus cases and outbreaks across
Europe, as provided by an email survey (left) and as reported to the FBVE
database (right). Numbers of reports in the email survey were partly estimates,
number of reports in the FBVE database are counts.
1Data of number of samples and genotypes not yet in the FBVE
sequence database, but sent by email
||data via email network
||in FBVE databases
|Increasing NoV activity in October and or November
or week 40-48?
||Numbers of outbreaks/ cases in Oct and Nov reported
after email request for data
||Basis of information
||Outbreaks in Oct and Nov in FBVE database
||Most recent genetic information in Bionumerics
||Genotypes/variants found in Oct and Nov
||lab database national
||surveill. database national
|| 184 outbreaks
|| 514 outbreaks
||4 G II.4 of which one variant 2006 b and 3 variant
2006a, and 4 other genotypes
|| 249 lab samples
|| 38 lab samples
|| 222 lab samples
||2 II.4, both variant 2006a1
|| 2 outbreaks
||1 II.4, variant 2006a
||~ 120 cases
||~ 10 cases
||~ 10 cases
|| 2 outbreaks
||2 II.4, variant 2006a , 1 other genotype
|England and Wales3
||768 outbreaks and round 756 lab samples
||83 outbreaks and 281 lab samples
||374 outbreaks and 682 lab samples
||43 G II.4 of which 20 2006a, 11 2006b and 12 non
a or b
15 non G II.41*
||7 G II.4 of which 5 variant 2006b and 2 2006a
|| 1 G II.4 variant 2006a, 1 other genotype
||26 G II.4 of which 19 2006a and 7 2006b
||~ 160 cases
||~ 65 cases
||~ 35 cases
||~ 400 cases
||~ 50 cases
||~ 350 cases
||1 G II.4, variant 2006a
2Data from Valencia and Catalonia
3Outbreaks reported from virus reference laboratory only. Laboratory
data are from England and Wales, these data will include outbreaks and sporadic
cases. The routine laboratory data cannot be linked to the data from the reference
The norovirus isolates causing 108 outbreaks which started in October
and November 2006 have been characterised, and 87 (81%) belonged to genotype
G.II 4, which has been the predominant genotype in recent years. Twenty-one
(19%) belonged to other genotypes. Of the 87 G II.4 isolates characterised,
51 (47%) were G II.4 new variant 2006a and 24 (22%) were variant 2006b1.
Twelve G II.4 isolates (11%) could not be assigned to a variant.
All norovirus outbreak isolates which were reported to FBVE sequence database
in the seasons 2004/2005, 2005/2006 and the present season so far are shown
(Figure). The first new variants of genotype GII.4 2006 appeared during
the 2005/2006 season, and became the predominant strain in summer 2006.
For variant 2006a, the first entry in the database is from an outbreak or
case in England in 2005. The first 2006b variant was reported from Spain
in December 2005 after an outbreak in a residential institution. In the
spring of 2006, this variant was found to be circulating widely, causing
at least 45 outbreaks of norovirus illness on cruise ships sailing across
Europe. It is believed that the emergence of the variants 2006a and 2006b
and the increase in outbreaks on cruise ships might well be the forewarning
of a very active norovirus season. This prediction is based on observations
in 1996, 2002 and 2004, when the appearance of new variants within genotype
GII.4 coincided with high levels of outbreak reporting worldwide [1,2,4].
Figure. Genotypes/variants in seasons 2004/5, 2005/6
and the start of 2006/7
Using all genetic information in the Bionumerics database:
- from outbreaks and from sequences submitted without background data (this
last group is small)
- from sequences of part of the polymerase gene (ORF 1) and 2 different
non overlapping regions of the capsid gene (ORF2).
2006/2007 norovirus season likely to see high activity
The different country reports indicate that the norovirus season has already
started in most areas. As predicted, 2006/2007 is likely to be a highly
active norovirus season, with the new variants of genotype G II.4 2006 being
predominant . It is therefore recommended that hospitals and nursing
homes inform their staff about the possibility of norovirus outbreaks and
provide information on the clinical presentation. They should also consult
their outbreak protocols, adopt them if necessary and strengthen preventive
measures, in order to be prepared for the present outbreak season.
The data provided in response to this email survey come from local datasets,
and are not (yet) visible in the FBVE database. The FBVE network maintains
a web-based database to which 13 national authorities report norovirus outbreaks,
along with epidemiological and laboratory data. The average delay between
the onset of an outbreak and the reporting of this outbreak to the FBVE
database is quite long. For the outbreaks reported in the quarterly period
of July to September 2006, the average delay was 111 days, ranging from
23 days (Sweden) to 436 days (Italy). As a result, in its present form,
the FBVE database can not be used to compare reports from Germany and Hungary
with the rest of the European situation. Since typing norovirus strains
takes some time, there is limited information on the circulating noroviruses
at the moment. A complete comparison will be possible towards the end of
*Correction 15 December. The original text incorrectly stated
'15 non G II.42'
Footnote. Comparisons of genome sequences to determine if norovirus
outbreak strains elsewhere belong to the same new variant lineage can be
done via an open access strain matching system (http://www.rivm.nl/bnwww).
This was established by the FBVE network to allow harmonized sequence comparisons
worldwide for commonly used genome regions (follow the links to ‘Food-borne
viruses in Europe’ and ‘quick typing database’. Requests for strain comparison
can also be sent to email@example.com).
- Bull RA, Tu ET, McIver CJ, Rawlinson WD, White PA. Emergence of a new
norovirus genotype II.4 variant associated with global outbreaks of gastroenteritis.
J Clin Microbiol. 2006 Feb;44(2):327-33.
- Lopman B, Vennema H, Kohli E, Pothier P, Sanchez A, Negredo A, et al.
Increase in viral gastroenteritis outbreaks in Europe and epidemic spread
of new norovirus variant. Lancet. 2004 Feb 28;363(9410):682-8.
- Koopmans M, Harris J, Verhoef L, Depoortere E, Takkinen J, Coulombier
D; International Outbreak Investigation Team. European investigation into
recent norovirus outbreaks on cruise ships: update. Euro Surveill 2006;
11(7) E060706.5 (http://www.eurosurveillance.org/ew/2006/060706.asp#5)
- Noel JS, Fankhauser RL, Ando T, Monroe SS, Glass RI. Identification of
a distinct strain of “Norwalk-like Viruses” having a global distribution.
J Infect Dis. 1999 Jun;179(6):1334-44.
- Takkinen J. Recent norovirus outbreaks on river and seagoing cruise ships
in Europe. Euro Surveill 2006;11(6):E060615.2. Available from: http://www.eurosurveillance.org/ew/2006/060615.asp#2
- RKI: Norovirus-Gastroenteritiden haben in den letzten Wochen deutlich
zugenommen - steht eine neue Winterepidemie bevor? Epid Bull 2006;48:427-429.
- Verhoef L, Depoortere E, Vennema H, Duizer E, Kroneman A, Harris J, et
al, on behalf of the Foodborne Viruses in Europe network. Norovirus outbreaks
on cruise ships sailing in European waters: what is the underlying cause?
(manuscript in preparation 2006).
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