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In 2009, the number of foodborne norovirus outbreaks in Finland seemed markedly high, and many outbreaks seemed to be linked to imported frozen raspberries. We reviewed the data regarding all notified foodborne outbreaks in 2009 in Finland in order to assess the magnitude of the problem and to summarize the information on raspberry–linked outbreaks. Between March and August, 13 norovirus outbreaks affecting about 900 people could be linked to imported frozen raspberries. Two raspberry samples corresponding to two batches of raspberries were positive for norovirus. These two batches proved to have been the likely source in six of the 13 outbreaks. Analytical studies had not been conducted for six outbreaks, and virological test results were inconclusive in two. However, combining epidemiological and microbiological methods often enabled finding the source, as exemplified in investigation of a large school outbreak. To ensure prompt control measures in similar situations in the future, both aspects of outbreak investigations should be strengthened.

EuroRotaNet, a laboratory network, was established in order to determine the diversity of co-circulating rotavirus strains in Europe over three or more rotavirus seasons from 2006/2007 and currently includes 16 countries. This report highlights the tremendous diversity of rotavirus strains co-circulating in the European population during three years of surveillance since 2006/2007 and points to the possible origins of these strains including genetic reassortment and interspecies transmission. Furthermore, the ability of the network to identify strains circulating with an incidence of ⩾1% allowed the identification of possible emerging strains such as G8 and G12 since the beginning of the study; analysis of recent data indicates their increased incidence. The introduction of universal rotavirus vaccination in at least two of the participating countries, and partial vaccine coverage in some others may provide data on diversity driven by vaccine introduction and possible strain replacement in Europe.

An inappropriate cross-connection between sewage- and drinking-water pipelines contaminated tap water in a Finnish town, resulting in an extensive waterborne gastroenteritis outbreak in this developed country. According to a database and a line-list, altogether 1222 subjects sought medical care as a result of this exposure. Seven pathogens were found in patient samples of those who sought treatment. To establish the true disease burden from this exposure, we undertook a population-based questionnaire investigation with a control population, infrequently used to study waterborne outbreaks. The study covered three areas, contaminated and uncontaminated parts of the town and a control town. An estimated 8453 residents fell ill during the outbreak, the excess number of illnesses being 6501. Attack rates were 53% [95% confidence interval (CI) 49·5–56·4] in the contaminated area, 15·6% (95% CI 13·1–18·5) in the uncontaminated area and 6·5% (95% CI 4·8–8·8) in the control population. Using a control population allowed us to differentiate baseline morbidity from the observed morbidity caused by the water contamination, thus enabling a more accurate estimate of the disease burden of this outbreak.

BackgroundThe first European rotavirus surveillance network, EuroRotaNet, comprising 16 laboratories in 15 European countries, has been established MethodsFecal samples from gastroenteritis cases positive for group A rotavirus antigen were collected from multiple European countries from 2005 to mid-2008 and were subjected to G and P genotyping. Epidemiological data collected included age, sex, geographical location, setting, dates of onset and sample collection, and clinical symptoms ResultsA total of 8879 rotavirus-positive samples were characterized: 2129 cases were from the 2005–2006 season, 4030 from the 2006–2007 season, and 2720 from the ongoing 2007–2008 season. A total of 30 different G and P type combinations of strains circulated in the region from 2005 through 2008. Of these strains, 90% had genotypes commonly associated with human infections—G1P[8], G2P[4], G3P[8], G4P[8], and G9P[8]—and 1.37% represented potential zoonotic introductions. G1P[8] remained the most prevalent genotype in Europe as a whole, but the incidence of infection with G1P[8] rotavirus strains was <50% overall, and all 3 seasons were characterized by a significant diversity of cocirculating strains. The peak incidence of rotavirus infection occurred from January through May, and 81% of case patients were aged <2.5 years ConclusionsData gathered through EuroRotaNet will provide valuable background information on the rotavirus strain diversity in Europe before the introduction of rotavirus vaccines, and the network will provide a robust method for surveillance during vaccine implementation

In August 2012, an outbreak of gastroenteritis occurred among 88 persons attending a wedding reception at a resort/activity centre in Ylöjärvi, Finland. Of 39 interviewed guests, 23 met the case definition. Two persons were hospitalized. Epidemiological, laboratory and environmental investigations were conducted to characterize the outbreak and to recommend control measures. Investigation confirmed the presence of a new strain of norovirus GII.4 Sydney variant in stool specimens obtained from two wedding guests and on several environmental surfaces in the centre. In the questionnaire study, none of the foods or beverages served during the reception were significantly associated with the illness. Additional cases of gastroenteritis that occurred at the centre before and after the wedding reception supported the hypothesis of environmental transmission of norovirus. After thorough cleansing and disinfection and 1 week's quarantine, no new cases with symptoms typical for norovirus infection were identified at the centre.

Multiple gastroenteritis outbreaks occurred between 25 and 31 July 2006 in 10 workplace canteens in south-western Finland. One vegetable processing plant provided raw vegetables to all the canteens. We conducted cohort studies in the three most visited canteens and environmental investigations in the kitchens and the plant. Patients' stools, food, water and environmental samples were tested for enteric bacteria and viruses. Of the three canteens, 150/273 respondents (response rate 82%) had gastroenteritis. Consumption of mixed raw vegetables was significantly associated with the illness but no single vegetable explains the outbreak. An identical norovirus GII.1 genotype was detected from all genotyped patient samples. Water, food, and environmental samples were negative for norovirus. The facilities had appropriate hygienic conditions and no staff member had gastroenteritis prior to the outbreak. Tracing back the vegetables to the farm level proved unsuccessful. This was the largest foodborne norovirus outbreak in Finland.

ABSTRACTBackground The food-borne viruses in Europe (FBVE) network database was established in 1999 to monitor trends in outbreaks of gastroenteritis due to noroviruses (NoVs), to identify major transmission routes of NoV infections within and between participating countries and to detect diffuse international food-borne outbreaks. Methods We reviewed the total of 9430 NoV outbreak reports from 13 countries with date of onset between 1 January 2002 and 1 January 2007 for representativeness, completeness and timeliness against these objectives. Results Rates of reporting ranged from a yearly average of 1.8 in 2003 to 11.6 in 2006. Completeness of reporting of an agreed minimum dataset improved over the years, both for epidemiological and virological data. For the 10 countries that provided integrated (epidemiological AND virological) reporting over the 5-year period, the completeness of the minimum dataset rose from 15% in 2003 to 48% in 2006. Two countries have not been able to combine both data types due to the structure of the national surveillance system (England and Wales and Germany). Timeliness of reporting (median days between the onset of an outbreak and the date of reporting to the FBVE database) differed greatly between countries, but gradually improved to 47 days in 2006. Conclusion The outbreaks reported to the FBVE reflect the lack of standardization of surveillance systems across Europe, making direct comparison of data between countries difficult. However, trends in reported outbreaks per country, distribution of NoV genotypes, and detection of diffuse international outbreaks were used as background data in acute questions about NoV illness and the changing genotype distribution during the 5-year period, shown to be of added value. Integrated reporting is essential for these objectives, but could be limited to sentinel countries with surveillance systems that allow this integration. For successful intervention in case of diffuse international outbreaks, completeness and timeliness of reporting would need to be improved and expanded to countries that presently do not participate.

In July 2001, an outbreak of gastroenteritis occurred in Helsinki among children and adults after bathing in an outdoor wading pool. The epidemiological survey revealed that at least 242 persons were affected. Microbiological testing of both patient stool samples and of the pool water revealed the presence of two different gastroenteritis viruses: a norovirus (NV) and an astrovirus. Amplicon sequencing of the NV samples showed nucleotide sequence identity between the virus from patients and the water. After changing the pool water and the sand at the bottom of the pool followed by shock chlorination, no virus could be detected in the water. However, NV was continuously detected in the water outlet well as much as 8 months after the incident. Here we show how molecular methods aided in tracing the source of the epidemic and in finding the causative pathogens both in patients and in the environment.

In April 1988, an outbreak of gastroenteritis occurred among employees in a large company in Helsinki, Finland. A retrospective cohort study, using a self-administered questionnaire, was carried out to ascertain the cause and extent of the outbreak. To meet the case definition, employees had to have had diarrhoea and/or vomiting since 2 April, 1998. A subanalysis was made in the biggest office, consisting of 360 employees, of whom 204 (57%) completed the questionnaire. Of these 108 (53%) met the case definition. Employees who had eaten raspberry dressing were more likely to meet the case definition than those who had not (Attack Rate (AR) 65% versus AR 18% Relative Risk, (RR) 3·7, 95%, Confidence Intervals (CI) 2·0–6·7). Four stool specimens obtained from affected kitchen staff who had all eaten the raspberry dressing and who had all become ill simultaneously with the employees were positive by polymerase chain reaction (PCR) for calicivirus. The data suggest that the primary source of the outbreak was imported frozen raspberries contaminated by calicivirus.

An outbreak of Norwalk-like calicivirus (NLV) gastroenteritis occurred in a rehabilitation centre in southern Finland between December 1999 and February 2000. An epidemiological investigation was conducted to determine the source and extent of the outbreak. More than 300 guests and staff members became ill during the outbreak. No food or activity in the centre could be linked epidemiologically to illness. NLV genogroup II was detected by RT–PCR in stool samples of symptomatic guests and employees. All strains reacted similarly with the microplate hybridization probe panel and showed the same nucleotide sequence, indicating that they represented the same NLV strain. Food and water samples were negative for NLV, whereas NLV was detected in three environmental specimens. The strains from patients and environment were identical based on microplate hybridization probes, suggesting that environmental contamination may have been important for the spread of calicivirus and the protracted course of the outbreak.