Increase in viral gastroenteritis outbreaks in Europe and epidemic spread of new norovirus variant.
BACKGROUND
Highly publicised outbreaks of norovirus gastroenteritis in hospitals in the UK and Ireland and cruise ships in the USA sparked speculation about whether this reported activity was unusual.


METHODS
We analysed data collected through a collaborative research and surveillance network of viral gastroenteritis in ten European countries (England and Wales were analysed as one region). We compiled data on total number of outbreaks by month, and compared genetic sequences from the isolated viruses. Data were compared with historic data from a systematic retrospective review of surveillance systems and with a central database of viral sequences.


RESULTS
Three regions (England and Wales, Germany, and the Netherlands) had sustained epidemiological and viral characterisation data from 1995 to 2002. In all three, we noted a striking increase in norovirus outbreaks in 2002 that coincided with the detection and emergence of a new predominant norovirus variant of genogroup II4, which had a consistent mutation in the polymerase gene. Eight of nine regions had an annual peak in 2002 and the new genogroup II4 variant was detected in nine countries. Also, the detection of the new variant preceded an atypical spring and summer peak of outbreaks in three countries.


CONCLUSIONS
Our data from ten European countries show a striking increase and unusual seasonal pattern of norovirus gastroenteritis in 2002 that occurred concurrently with the emergence of a novel genetic variant. In addition to showing the added value of an international network for viral gastroenteritis outbreaks, these observations raise questions about the biological properties of the variant and the mechanisms for its rapid dissemination.
Health Protection Agency, London, UK.
Ben
B
Lopman
Harry
H
Vennema
Evelyne
E
Kohli
Pierre
P
Pothier
Alicia
A
Sanchez
Anabel
A
Negredo
Javier
J
Buesa
Eckart
E
Schreier
Mark
M
Reacher
David
D
Brown
Jim
J
Gray
Miren
M
Iturriza
Chris
C
Gallimore
Blenda
B
Bottiger
Kjell-Olof
KO
Hedlund
Maria
M
Torvén
Carl-Henrik
CH
von Bonsdorff
Leena
L
Maunula
Mateja
M
Poljsak-Prijatelj
Janet
J
Zimsek
Gábor
G
Reuter
György
G
Szücs
Béla
B
Melegh
Lennart
L
Svennson
Yvonne
Y
van Duijnhoven
Marion
M
Koopmans
D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D005516:Food Microbiology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology; D014644:Genetic Variation; D006801:Humans; D009154:Mutation / Q000235:genetics; D029322:Norovirus / Q000235:genetics / Q000302:isolation & purification*; D011159:Population Surveillance; D012189:Retrospective Studies; D012621:Seasons