Norovirus outbreak at an international scout jamboree in the
Netherlands, July-August 2004: international alert
A norovirus outbreak at an international scout summer camp
in the Netherlands has affected approximately 250 people (scouts and staff
members) out of 4500 participants. Thirty five participants were ill on the
last night, and two children were ill before the start of the camp on 26 July.
Symptoms have generally been mild with most patients experiencing vomiting
and diarrhoea, although 47 patients were admitted to a local hospital for
rehydration. Infection control measures have been put in place in order
to contain the outbreak. The regional municipal health service (GGD Hart
voor Brabant) has been involved in managing the outbreak. Norovirus has
been epidemiologically implicated as the causative agent.
The presence of norovirus was confirmed in vomit samples at the Rijksinstituut
voor Volksgezondheid en Milieu (RIVM, National Institute of Public Health)
using a standard RT-PCR protocol. Faecal samples are currently under investigation.
The two children, one from Scotland and one from the Netherlands, who are
reported to have been ill before joining the summer camp may be the index
cases, but we have not yet been able to obtain and analyse samples from
these two children. From the first series of positive samples, 4 noroviruses
have been sequenced for typing, and this yielded three norovirus variants:
NoV GGI.4 ("Malta"), NoV GGI.5 ("Butlins") and a NoV
GGII.4 ("Grimsby"). Sequencing of other positive samples (mostly
vomit) from the outbreak is in progress.
In this outbreak, there are clear indications of multiple introductions
of viruses by sick people., Generally, the presence of more than one virus
strain in an outbreak is indicative of food- or waterborne introduction.
Preliminary epidemiological data do not implicate food as a vector in this
outbreak. The scouts had swum in a recreational lake that complied with
European standards for faecal contamination. Currently, water samples are
being analysed for the presence of norovirus. Questionnaires have been distributed
among the scouts, and data collection and analysis is ongoing.
The national jamboree campsite hosted over 3700 participants (between 11-17
years of age) and about 800 staff members. Besides a large number of Dutch
participants, about 1000 scouts came from 31 other countries, including
Belgium, the United Kingdom, Germany, Ukraine, Serbia, Kosovo, Turkey, the
United States, Australia, Hong Kong, Indonesia, Pakistan, Algeria, Tunisia,
Nigeria and Kenya. The jamboree ended on 5 August and several more cases
have been reported in the past seven days. Since the shedding of norovirus
continues after recovery from illness, and can also occur in the absence
of illness, thorough hygienic measures, emphasising handwashing, of all
participants leaving the camp will be essential to reduce further spread
of the virus.
Suspected cases connected with this outbreak in any country maybe reported
to Erwin Duizer (email Erwin.Duizer@rivm.nl,
telephone +31 30 274 4142, fax +31 30 274 4418)
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