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Published Date: 2005-06-24 23:50:00
Subject: PRO/EDR> Viral gastroenteritis update 2005 (11)
Archive Number: 20050624.1768

VIRAL GASTROENTERITIS UPDATE 2005 (11)
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International Society for Infectious Diseases
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In this update:
[1] Norovirus, floodwater - Austria
[2] Norovirus, frozen raspberries - Denmark
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[1] Norovirus, floodwater - Austria
Date: Thu 16 Jun 2005
From: ProMED-mail <promed@promedmail.org>
Source: Eurosurveillance Weekly 2005; 10(24): 16 Jun [edited]
<http://www.eurosurveillance.org/ew/2005/050616.asp>

Outbreak of norovirus infection linked to contaminated floodwater,
Salzburg, 2005
------------------------------------------------------
An outbreak of gastrointestinal illness in American tourists in May-June
2005 that was first thought to be foodborne has been linked to direct
exposure to floodwater contaminated with raw sewage. On 1 Jun 2005, ORF
(the Austrian Broadcasting Company) reported that 26 out of 36 American
tourists who had eaten dinner in a well-known restaurant in Salzburg had
fallen ill. According to the news report, 10 of the ill tourists had
presented to a local hospital, triggering an outbreak investigation by the
local health authorities, who assumed salmonella to be the causative agent.
On 2 Jun 2005 the Oesterreichische Agentur fuer Gesundheit und
Ernaehrungssicherheit (the Austrian Agency for Health and Food Safety,
AGES) requested stool samples from the local hospital laboratory, to test
for norovirus at the AGES norovirus reference laboratory. The local
hospital had already tested the stool samples for salmonella and
campylobacter, and all samples were negative after 48 hours. On 3 Jun 2005,
reverse transcriptase-polymerase chain reaction (RT-PCR) testing of 7
specimens revealed 4 samples to be positive for norovirus, including 2
mixed infections with different genotypes. The high number of cases
reportedly occurring on a single day indicated a foodborne norovirus
outbreak (1) and the occurrence of mixed infection suggested bivalve
molluscan shellfish such as oysters, or salad vegetables grown in
sewage-contaminated soil as a probable source (2). The ability of molluscs
to concentrate viral pathogens by filtration feeding makes them a known
source of viral outbreaks and may explain the occurrence of mixed
infections. An epidemiological investigation was initiated to identify the
outbreak cause.
On 3 Jun 2005, the outbreak investigation team gave a standardised
questionnaire about recent gastrointestinal illness to the tourist group.
All those tourists who had been ill were now recovered, and the group was
staying in Vienna. A detailed food exposure history (especially for raw
seafood) was ascertained for the previous 7 days. The group consisted of 60
tourists (mean age 69 years), 2 bus drivers and 2 tour guides. A case was
defined as member of the group who had diarrhoea or vomiting accompanied by
at least one other symptom (nausea, abdominal pain, vomiting or diarrhoea)
since 30 May 2005.
Of the 64 people interviewed, 49 (77 per cent) met the outbreak case
definition. The illness duration ranged from less than 1 day to 4 days. The
first 4 cases occurred on 31 May, followed by 36 cases on 1 June, 2 cases
on 2 June, and 7 on 3 June. The questionnaire analyses did not implicate
any particular foodstuff in this outbreak. Only one person had eaten raw
seafood, but remained healthy; raw seafood was therefore excluded as a
common link among the cases. However, the interviews revealed that the
entire tourist group had been exposed to faecally contaminated water on the
day of arrival in Salzburg, after staying in Italy for 2 days. While the
group was checking into a hotel on the afternoon of 30 May, there was
extremely heavy rainfall in Salzburg, which resulted in flooding inside the
hotel. Before the group was transferred to alternative accommodation, they
helped staff to clear water from the affected hotel, and they were heavily
exposed to flood water from the hotel sanitation system, which they
reported included visible pieces of toilet paper and faeces.
The epidemiological investigation strongly suggests that this norovirus
outbreak was due to direct exposure to sewage water due to flooding on the
evening of 30 May, and that there was no connection to the dinner consumed
at the restaurant. The hotel had been promptly cleaned and disinfected so
no raw sewage material was available for testing. However, the hypothesis
for the cause of the outbreak was strengthened when additional cases
compatible with norovirus infection were detected on June 5: 6 of the 10
firefighters who pumped flood water from the affected hotel on the night of
30-31 May fell ill with vomiting or diarrhoea (stool specimens taken on
June 7 tested negative for norovirus).
Flooding is associated with an increased risk of infection, but this risk
is low unless there is significant population displacement or water sources
are compromised (i.e. drinking water is contaminated). Neither of these
factors was present in Salzburg. The waterborne norovirus infections
described here were contracted through direct contact with water polluted
with human faeces, causing a point source outbreak followed by
person-to-person transmission.
References
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(1) Cotterelle B, Drougard C, Rolland J, Becamel M, Boudon M, Pinede S, et
al. Outbreak of norovirus infection associated with the consumption of
frozen raspberries, France, March 2005. Eurosurveillance Weekly 2005;
10(17): 28/04/2005. (<http://www.eurosurveillance.org/ew/2005/050428.asp#1>)
(2) Doyle A, Barataud D, Gallay A, Thiolet JM, Le Guyager S, Kohli E, et
al. Norovirus foodborne outbreaks associated with the consumption of
oysters from the Etang de Thau, France, December 2002. Euro Surveill 2004;
9(3): 24-6. (<http://www.eurosurveillance.org/ew/2005/050428.asp#1>)
[byline: Daniela Schmid, Ingeborg Lederer, Peter Much, Anna-Margaretha
Pichler and Franz Allerberger (<Franz.Allerberger@ages.at>. Centre for
Infectious Diseases Epidemiology, Oesterreichische Agentur fuer Gesundheit
und Ernaehrungssicherheit, Vienna, Austria]
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[2] Norovirus, frozen raspberries - Denmark
Date: Thu 23 Jun 2005
From: ProMED-mail <promed@promedmail.org>
Source: Eurosurveillance Weekly 2005; 10(25): 23 Jun [edited]
<http://www.eurosurveillance.org/ew/2005/050623.asp>

2 outbreaks of norovirus infection linked to consumption of imported frozen
r, Denmark, May-June 2005
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On the weekend of 21 to 22 May 2005, it was reported that 101 patients and
76 employees at the 2 Aalborg Hospitals, South and North, in Northern
Jutland, were ill with vomiting and diarrhoea. In the following 4 days, a
further 43 patients and 52 employees, as well as 4 relatives, were reported
to be ill. Because of simultaneous outbreaks in the 2 physically separated
hospitals, a foodborne source of infection was suspected. Cohort isolation
of the sick patients was implemented, and some admissions, as well as a
total of 43 operations, were cancelled. Sick employees were requested not
to turn up for work until they had been well for at least 24 hours (48
hours for kitchen staff). In order to reduce the risk of infection, kitchen
areas were disinfected and cleaning staff were instructed in disinfection
of toilet areas. Infection control nurses and the Regional Food
Inspectorate provided disinfection guidelines, for which a disinfectant
that is active against norovirus was used.
Case control studies were conducted among a total of 120 employees and
inpatients at the hospitals. The studies showed that the sick employees had
all been at work on Thursday (odds ratio (OR) 15; 95 per cent confidence
interval (CI) 3.4 to 71) and that the consumption of a fromage blanc (fresh
cheese) dessert containing frozen pieces of raspberries in the canteen that
day was associated with an increased risk of disease (OR infinite, lower
confidence limit 3.4). Consumption of the same dessert with raspberries was
also associated with illness in patients (OR 6.2; 95 per cent CI 1.6 to
26). The suspicion of a norovirus infection was confirmed by the results of
investigation of faecal specimens.
Outbreak on Sjaelland
---------------------
From 3 Jun 2005, several cases of gastrointestinal infection were also
registered among the elderly in several areas in Sjaelland, and in the
Greater Copenhagen area. The patients had received food from one particular
food caterer supplying 12 municipalities with a "meals on wheels" service
as part of a home nursing scheme. On the basis of the experience from
Aalborg, the possibility that this was another norovirus outbreak was
thought to be likely, and the most likely source of infection a raspberry
dessert that had been served to around 1100 people between Wed 1 Jun and
Fri 3 Jun 2005. The frozen raspberries used were bought from the same
importer that supplied the raspberries implicated in the outbreak in the
Aalborg Hospitals.
As of 23 Jun 2005, there appear to be at least 289 cases associated with
this 2nd outbreak. Several stool specimens collected from patients at
Sjaelland were found positive for norovirus.
Discussion
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This is a preliminary report of large foodborne outbreaks of norovirus
infection associated with consumption of desserts made from frozen
raspberries. The overall extent of these outbreaks, including secondary
transmission, will be elucidated in ongoing investigations. Microbiological
analyses of the raspberries as well as further analyses of stool specimens,
including genotyping of norovirus, are also in progress. Preliminary
results suggest that there may be more than one genotype involved.
It is important to note that the source of infection was recognised rapidly
due to the swift response from the Medical Officer of Health, the Regional
Food Inspectorate and the infection control department at Aalborg Hospital.
Unfortunately, immediate withdrawal of the frozen raspberries from the
market was not immediately implemented, and this delay resulted in another
outbreak in Sjaelland that has afflicted at least 289 people in a very
vulnerable age group. This outbreak could have been prevented by a more
efficient recall.
After the cases at Sjaelland, the Danish Veterinary and Food Administration
reinforced the recall, and the Danish importer has now withdrawn all
similarly sourced raspberries from the market. The raspberries were
imported from Poland, and were not distributed to ordinary retail outlets.
It is not known if the raspberries were distributed to other countries.
Immediately after the recognition of the outbreak in Aalborg, the
Food-borne viruses in Europe network (FBVE,
<http://www.eufoodborneviruses.co.uk>) was informed, and international
warnings were sent through both the European Early Warning and Response
System (EWRS) and the Rapid Alert System for Food and Feed (RASFF,
<http://europa.eu.int/comm/food/food/rapidalert/index_en.htm>).
Raspberries have previously been associated with outbreaks of norovirus,
most recently in March 2005, when a French school was affected [1].
However, the same producer was not involved as in the Danish outbreaks, and
the strain in the outbreak in France (genogroup I genotype 5; Musgrove
strain) has not been found so far in the recent Danish outbreaks.
Reference
---------
(1) Cotterelle B, Drougard C, Rolland J, Becamel M, Boudon M, Pinede S, et
al. Outbreak of norovirus infection associated with the consumption of
frozen raspberries, France, March 2005. Eurosurveillance Weekly 2005;
10(17): 28/04/2005. (<http://www.eurosurveillance.org/ew/2005/050428.asp#1>)
[Byline: Birgitte Korsager1, Susanne Hede2, Henrik Boggild3, Blenda
Bottiger4, and Kare Molbak5 (<krm@ssi.dk>
1 Department of Clinical Microbiology, Aalborg Sygehus, Denmark
2 Regional Food Inspectorate, Northern Jutland, Aalborg, Denmark
3 Medical Officer of Northern Jutland County, Aalborg, Denmark
4 Department of Virology, Statens Serum Institut, Copenhagen, Denmark
5 Department of Epidemiology, Statens Serum Institut, Copenhagen, Denmark]
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