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In 2016, we reviewed preventive control measures for secondary transmission of Shiga-toxin producing Escherichia coli (STEC) in humans in European Union (EU)/European Free Trade Association (EEA) countries to inform the revision of the respective Norwegian guidelines which at that time did not accommodate for the varying pathogenic potential of STEC. We interviewed public health experts from EU/EEA institutes, using a semi-structured questionnaire. We revised the Norwegian guidelines using a risk-based approach informed by the new scientific evidence on risk factors for HUS and the survey results. All 13 (42%) participating countries tested STEC for Shiga toxin (stx) 1, stx2 and eae (encoding intimin). Five countries differentiated their control measures based on clinical and/or microbiological case characteristics, but only Denmark based their measures on routinely conducted stx subtyping. In all countries, but Norway, clearance was obtained with ⩽3 negative STEC specimens. After this review, Norway revised the STEC guidelines and recommended only follow-up of cases infected with high-virulent STEC (determined by microbiological and clinical information); clearance is obtained with three negative specimens. Implementation of the revised Norwegian guidelines will lead to a decrease of STEC cases needing follow-up and clearance, and will reduce the burden of unnecessary public health measures and the socioeconomic impact on cases. This review of guidelines could assist other countries in adapting their STEC control measures. [ABSTRACT FROM AUTHOR]

In Norway, incidence of sporadic domestically acquired salmonellosis is low, and most frequently due to Salmonalla Typhimurium. We investigated the risk factors for sporadic Salmonella infections in Norway to improve control and prevention measures. Surveillance data for all Salmonella infections from 2000 to 2015 were analysed for seasonality and proportion associated with domestic reservoirs, hedgehogs and wild birds. A prospective case-control study was conducted from 2010 to 2012 by recruiting cases from the Norwegian Surveillance System for Communicable Diseases and controls from the Norwegian Population Registry (389 cases and 1500 controls). Univariable analyses using logistic regression were conducted and a multivariable model was developed using regularised/penalised logistic regression. In univariable analysis, eating snow, dirt, sand or playing in a sandbox (aOR 4.14; CI 2.15-7.97) was associated with salmonellosis. This was also the only exposure significantly associated with illness in the multivariable model. Since 2004, 34.2% (n = 354) of S. Typhimuirum cases had an MLVA profile linked to a domestic reservoir. A seasonal trend with a peak in August for all Salmonella types and in February for S. Typhimurium was observed. Indirect exposure to domestic reservoirs remains a source of salmonellosis in Norway, particularly for children. Information to the public about avoiding environmental exposure should be strengthened and initiatives to combat salmonellosis in the food chain should be reinforced. [ABSTRACT FROM AUTHOR]

In 2011, an outbreak of illness caused by Yersinia enterocolitica O:9 in Norway was linked to ready-to-eat salad mix, an unusual vehicle for this pathogen. The outbreak illustrates the need to characterize isolates of this organism, and reinforces the need for international traceback mechanisms for fresh produce. [ABSTRACT FROM AUTHOR]

Abstract Background On October 29th 2009 the health authorities in the city of Trondheim, Norway were alerted about a case of Shiga toxin-positive E. coli (STEC) O145 in a child with bloody diarrhoea attending a day-care centre. Symptomatic children in this day-care centre were sampled, thereby identifying three more cases. This initiated an outbreak investigation. Methods A case was defined as a child attending the day-care centre, in whom eae- and stx1- but not stx2-positive E. coli O145:H28 was diagnosed from a faecal sample, with multilocus variable number of tandem repeat analysis (MLVA) profile identical to the index isolate. All 61 children, a staff of 14 in the day-care centre, and 74 close contacts submitted faecal samples. Staff and parents were interviewed about cases' exposure to foods and animals. Faecal samples from 31 ewes from a sheep herd to which the children were exposed were analyzed for E. coli O145. Results Sixteen cases were identified, from which nine presented diarrhoea but not haemolytic uremic syndrome (HUS). The attack rate was 0.26, and varied between age groups (0.13-0.40) and between the three day-care centre departments (0.20-0.50), and was significantly higher amongst the youngest children. Median duration of shedding was 20 days (0-71 days). Children were excluded from the day-care centre during shedding, requiring parents to take compassionate leave, estimated to be a minimum total of 406 days for all cases. Atypical enteropathogenic E. coli (aEPEC) were detected among 14 children other than cases. These isolates were genotypically different from the outbreak strain. Children in the day-care centre were exposed to faecal pollution from a sheep herd, but E. coli O145 was not detected in the sheep. Conclusions We report an outbreak of stx1- and eae-positive STEC O145:H28 infection with mild symptoms among children in a day-care centre. Extensive sampling showed occurrence of the outbreak strain as well as other STEC and aEPEC strains in the outbreak population. MLVA-typing of the STEC-isolates strongly indicates a common source of infection. The study describes epidemiological aspects and socioeconomic consequences of a non-O157 STEC outbreak, which are less commonly reported than O157 outbreaks.

Abstract Background In March 2007, the Norwegian Institute of Public Health was notified of Swedish individuals diagnosed with cryptosporidiosis after staying at a Norwegian hotel. In Norway, cryptosporidiosis is not reportable, and human infections are rarely diagnosed. Methods A questionnaire on illness and exposure history was e-mailed to seven organised groups who had visited the hotel in March. Cases were defined as persons with diarrhoea for more than two days or laboratory-confirmed cryptosporidiosis during or within two weeks of the hotel visit. The risk factor analysis was restricted to two groups with the highest attack rates (AR) and same hotel stay period. Local food safety authorities conducted environmental investigations. Results In total, 25 diarrhoeal cases (10 laboratory-confirmed) were identified among 89 respondents. Although environmental samples were negative, epidemiological data suggest an association with in-house water consumption. In one group, the AR was higher amongst consumers of water from hotel dispenser (relative risk [RR] = 3.0; 95% confidence interval [CI]: 0.9–9.8), tap water (RR = 2.3; CI: 0.9–5.8), and lower amongst commercial bottled water drinkers (RR = 0.6; CI: 0.4–1.0). Consumption of ice cubes was a risk-factor (RR = 7.1; CI: 1.1–45.7) in the two groups combined. Conclusion This outbreak would probably have remained undetected without the alert from Swedish health authorities, illustrating the difficulties in outbreak detection due to low health care seeking behaviour for diarrhoea and limited parasite diagnostics in Norway. Awareness of cryptosporidiosis should be raised amongst Norwegian medical personnel to improve case and outbreak detection, and possible risks related to in-house water systems should be assessed.

Abstract Background On 7 May 2007 the medical officer in Røros (population 5600) reported 15 patients with gastroenteritis. Three days later he estimated hundreds being ill. Untreated tap water from a groundwater source was suspected as the vehicle and chlorination was started 11 May. Campylobacter was isolated from patients' stool samples. We conducted an investigation to identify the source and describe the extent of the outbreak. Methods We undertook a retrospective cohort study among a random sample of customers of Røros and neighbouring Holtålen waterworks. Holtålen, which has a different water source, was used as a control city. We conducted telephone interviews to gather data on illness from all household members. One randomly selected household member was asked about detailed exposure history. The regional hospital laboratory tested patients' stools for enteropathogens. Campylobacter isolates were typed by AFLP for genetic similarity at the Norwegian Institute of Public Health. Local authorities conducted the environmental investigation. Results We identified 105 cases among 340 individuals from Røros and Holtålen (Attack Rate = 31%). Tap water consumption was the only exposure associated with illness. Among randomly selected household members from Røros, a dose-response relationship was observed in daily consumed glasses of tap water (χ2 for trend = 8.1, p = 0.004). Campylobacter with identical AFLP was isolated from 25 out of 26 submitted stool samples. No pathogens were detected in water samples. We identified several events that might have caused pressure fall and influx of contaminated water into the water distribution system. On two occasions, pressure fall was noticed and parts of the distribution system were outdated. Conclusion The investigation confirmed a waterborne outbreak of campylobacteriosis in Røros. Although no single event was identified as the cause of contamination, this outbreak illustrates the vulnerability of water distribution systems. Good quality source water alone is not enough to ensure water safety. For a better risk management, more focus should be put on the distribution system security. Waterworks personnel should monitor the pressure regularly; reduce the leakage by upgrading the distribution network and use chlorination when conducting maintenance work.

Objectives: We analysed hepatitis A (HepA) notifications and hospitalisations in Italy, the Netherlands, Norway, Spain, and Sweden for available periods between 1995 and 2014. We aimed to investigate whether decreasing HepA incidence is associated with increasing age at infection and worsening HepA presentation and to identify groups at risk of severe disease., Methods: We performed a retrospective cohort study including 36 734 notified and 36 849 hospitalised patients. We used negative binomial regressions to identify over time: i) trends in hospitalisation and notification rates; ii) proportion of hospitalised and notified patients aged ≥40 years; iii) proportion of "severe hospitalisations"; and iv) risk factors for severe hospitalisation., Results: During the study period both HepA notifications and hospitalisations decreased, with notification rates decreasing faster, patients aged ≥40 years increased, however, the proportion of severe HepA hospitalisations remained stable. Older patients and patients with comorbidities, particularly liver diseases, were more likely to experience severe disease., Conclusions: We used digitalised health information to confirm decreasing trends in HepA hospitalisations and notifications, and the increasing age of patients with HepA in Europe. We did not identify an increase in the severity of the clinical presentation of patients with HepA. Older patients with liver diseases are at increased risk of severe disease and should be prioritised for vaccination., Competing Interests: Conflict of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: To estimate the risk of hospitalization among reported cases of the Delta variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) compared with the Alpha variant in Norway, and the risk of hospitalization by vaccination status., Methods: A cohort study was conducted on laboratory-confirmed cases of SARS-CoV-2 in Norway, diagnosed between 3 May and 15 August 2021. Adjusted risk ratios (aRR) with 95% confidence intervals (CI) were calculated using multi-variable log-binomial regression, accounting for variant, vaccination status, demographic characteristics, week of sampling and underlying comorbidities., Results: In total, 7977 cases of the Delta variant and 12,078 cases of the Alpha variant were included in this study. Overall, 347 (1.7%) cases were hospitalized. The aRR of hospitalization for the Delta variant compared with the Alpha variant was 0.97 (95% CI 0.76-1.23). Partially vaccinated cases had a 72% reduced risk of hospitalization (95% CI 59-82%), and fully vaccinated cases had a 76% reduced risk of hospitalization (95% CI 61-85%) compared with unvaccinated cases., Conclusions: No difference was found between the risk of hospitalization for Delta cases and Alpha cases in Norway. The results of this study support the notion that partially and fully vaccinated cases are highly protected against hospitalization with coronavirus disease 2019., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

We included 39,524 COVID-19 Omicron and 51,481 Delta cases reported in Norway from December 2021 to January 2022. We estimated a 73% reduced risk of hospitalisation (adjusted hazard ratio: 0.27; 95% confidence interval: 0.20-0.36) for Omicron compared with Delta. Compared with unvaccinated groups, Omicron cases who had completed primary two-dose vaccination 7-179 days before diagnosis had a lower reduced risk than Delta (66% vs 93%). People vaccinated with three doses had a similar risk reduction (86% vs 88%).

In late November 2021, an outbreak of Omicron SARS-CoV-2 following a Christmas party with 117 attendees was detected in Oslo, Norway. We observed an attack rate of 74% and most cases developed symptoms. As at 13 December, none have been hospitalised. Most participants were 30-50 years old. Ninety-six percent of them were fully vaccinated. These findings corroborate reports that the Omicron variant may be more transmissible, and that vaccination may be less effective in preventing infection compared with Delta.

Introduction: Since their emergence, SARS-CoV-2 variants of concern (VOC) B.1.1.7 and B.1.351 have spread worldwide. We estimated the risk of hospitalisation and admission to an intensive care unit (ICU) for infections with B.1.1.7 and B.1.351 in Norway, compared to infections with non-VOC., Materials and Methods: Using linked individual-level data from national registries, we conducted a cohort study on laboratory-confirmed cases of SARS-CoV-2 in Norway diagnosed between 28 December 2020 and 2 May 2021. Variants were identified based on whole genome sequencing, partial sequencing by Sanger sequencing or PCR screening for selected targets. The outcome was hospitalisation or ICU admission. We calculated adjusted risk ratios (aRR) with 95% confidence intervals (CIs) using multivariable binomial regression to examine the association between SARS-CoV-2 variants B.1.1.7 and B.1.351 with i) hospital admission and ii) ICU admission compared to non-VOC., Results: We included 23,169 cases of B.1.1.7, 548 B.1.351 and 4,584 non-VOC. Overall, 1,017 cases were hospitalised (3.6%) and 206 admitted to ICU (0.7%). B.1.1.7 was associated with a 1.9-fold increased risk of hospitalisation (aRR 95%CI 1.6-2.3) and a 1.8-fold increased risk of ICU admission (aRR 95%CI 1.2-2.8) compared to non-VOC. Among hospitalised cases, no difference was found in the risk of ICU admission between B.1.1.7 and non-VOC. B.1.351 was associated with a 2.4-fold increased risk of hospitalisation (aRR 95%CI 1.7-3.3) and a 2.7-fold increased risk of ICU admission (aRR 95%CI 1.2-6.5) compared to non-VOC., Discussion: Our findings add to the growing evidence of a higher risk of severe disease among persons infected with B.1.1.7 or B.1.351. This highlights the importance of prevention and control measures to reduce transmission of these VOC in society, particularly ongoing vaccination programmes, and preparedness plans for hospital surge capacity., Competing Interests: The authors have declared that no competing interests exist.

BackgroundThe occupational risk of COVID-19 may be different in the first versus second epidemic wave.AimTo study whether employees in occupations that typically entail close contact with others were at higher risk of SARS-CoV-2 infection and COVID-19-related hospitalisation during the first and second epidemic wave before and after 18 July 2020, in Norway.MethodsWe included individuals in occupations working with patients, children, students, or customers using Standard Classification of Occupations (ISCO-08) codes. We compared residents (3,559,694 on 1 January 2020) in such occupations aged 20-70 years (mean: 44.1; standard deviation: 14.3 years; 51% men) to age-matched individuals in other professions using logistic regression adjusted for age, sex, birth country and marital status.ResultsNurses, physicians, dentists and physiotherapists had 2-3.5 times the odds of COVID-19 during the first wave when compared with others of working age. In the second wave, bartenders, waiters, food counter attendants, transport conductors, travel stewards, childcare workers, preschool and primary school teachers had ca 1.25-2 times the odds of infection. Bus, tram and taxi drivers had an increased odds of infection in both waves (odds ratio: 1.2-2.1). Occupation was of limited relevance for the odds of severe infection, here studied as hospitalisation with the disease.ConclusionOur findings from the entire Norwegian population may be of relevance to national and regional authorities in handling the epidemic. Also, we provide a knowledge foundation for more targeted future studies of lockdowns and disease control measures.

Climate change will lead to more extreme weather events in Europe. In Norway, little is known about how this will affect drinking water quality and population's health due to waterborne diseases. The aim of our work was to generate new knowledge on the effect of extreme weather conditions and climate change on drinking water and waterborne disease. In this respect we studied the relationship between temperature, precipitation and runoff events, raw and treated water quality, and gastroenteritis consultations in Norway in 2006-2014 to anticipate the risk with changing climate conditions. The main findings are positive associations between extreme weather events and raw water quality, but only few with treated drinking water. Increase in maximum temperature was associated with an increase in risk of disease among all ages and 15-64 years olds for the whole year. Heavy rain and high runoff were associated with a decrease in risk of gastroenteritis for different age groups and time periods throughout the year. No evidence was found that increase in precipitation and runoff trigger increased gastroenteritis outbreaks. Large waterworks in Norway currently seem to manage extreme weather events in preventing waterborne disease. However, with more extreme weather in the future, this may change. Therefore, modelling future climate scenarios is necessary to assess the need for improved water treatment capacity in a future climate., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

Background: Waterborne outbreaks are still a risk in high-income countries, and their early detection is crucial to limit their societal consequences. Although syndromic surveillance is widely used for the purpose of detecting outbreaks days earlier than traditional surveillance systems, evidence of the effectiveness of such systems is lacking. Thus, our objective was to conduct a systematic review of the effectiveness of syndromic surveillance to detect waterborne outbreaks., Method: We searched the Cochrane Library, Medline/PubMed, EMBASE, Scopus, and Web of Science for relevant published articles using a combination of the keywords 'drinking water', 'surveillance', and 'waterborne disease' for the period of 1990 to 2018. The references lists of the identified articles for full-text record assessment were screened, and searches in Google Scholar using the same key words were conducted. We assessed the risk of bias in the included articles using the ROBINS-I tool and PRECEPT for the cumulative body of evidence., Results: From the 1959 articles identified, we reviewed 52 articles, of which 18 met the eligibility criteria. Twelve were descriptive/analytical studies, whereas six were simulation studies. There is no clear evidence for syndromic surveillance in terms of the ability to detect waterborne outbreaks (low sensitivity and high specificity). However, one simulation study implied that multiple sources of signals combined with spatial information may increase the timeliness in detecting a waterborne outbreak and reduce false alarms., Conclusion: This review demonstrates that there is no conclusive evidence on the effectiveness of syndromic surveillance for the detection of waterborne outbreaks, thus suggesting the need to focus on primary prevention measures to reduce the risk of waterborne outbreaks. Future studies should investigate methods for combining health and environmental data with an assessment of needed financial and human resources for implementing such surveillance systems. In addition, a more critical thematic narrative synthesis on the most promising sources of data, and an assessment of the basis for arguments that joint analysis of different data or dimensions of data (e.g. spatial and temporal) might perform better, should be carried out., Trial Registration: PROSPERO: International prospective register of systematic reviews. 2019. CRD42019122332 ., (© 2021. The Author(s).)