Norovirus Outbreaks Research Articles

Notes from the Field: Multiple Cruise Ship Outbreaks of Norovirus Associated with Frozen Fruits and Berries - United States, 2019.

This investigation highlights the importance of acute gastroenteritis (AGE) surveillance at sea to identify contaminated foods at sea not yet implicated on land and to prevent transmission of AGE illness through U.S. ports.

Norovirus infections and knowledge, attitudes and practices in food safety among food handlers in an informal urban settlement, Kenya 2017

IntroductionA leading cause of acute gastroenteritis, norovirus can be transmitted by infected food handlers but norovirus outbreaks are not routinely investigated in Kenya. We estimated norovirus prevalence and associated factors among food handlers in an informal urban settlement in Nairobi, Kenya.MethodsWe conducted a cross-sectional survey among food handlers using pretested questionnaires and collected stool specimens from food handlers which were analyzed for norovirus by conventional PCR. We observed practices that allow norovirus transmission and surveyed respondents on knowledge, attitudes, and practices in food safety. We calculated odd ratios (OR) with 95% confidence intervals (CI) to identify factors associated with norovirus infection. Variables with p < 0.05 were included in multivariate logistic regression analysis to calculate adjusted OR and 95% CI.ResultsOf samples from 283 respondents, 43 (15.2%) tested positive for norovirus. Factors associated with norovirus detection were: reporting diarrhea and vomiting within the previous month (AOR = 5.7, 95% CI = 1.2–27.4), not knowing aerosols from infected persons can contaminate food (AOR = 6.5, 95% CI = 1.1–37.5), not knowing that a dirty chopping board can contaminate food (AOR = 26.1, 95% CI = 1.6–416.7), observing respondents touching food bare-handed (AOR = 3.7, 95% CI = 1.5–11.1), and working in premises without hand washing services (AOR = 20, 95% CI = 3.4–100.0).ConclusionThe norovirus infection was prevalent amongst food handlers and factors associated with infection were based on knowledge and practices of food hygiene. We recommend increased hygiene training and introduce more routine inclusion of norovirus testing in outbreaks in Kenya.

Influenza and norovirus outbreaks in an inpatient mental health setting: Analysis and strategies for successful containment

During the spring of 2019, an inpatient psychiatry unit at a large tertiary care hospital experienced two outbreaks between April 6 and May 7, first influenza A, with seven identified cases, followed by norovirus with three identified cases. This outbreak investigation examines the management of both outbreaks and highlights unique challenges, which may present in a mental health setting. While both outbreaks ultimately resulted in full recovery for all affected patients, considerations, such as impact to patient therapies, fomite transmission, shared spaces, access to psychiatric services and impact to mental health require innovative thinking. Unique outbreak management considerations, and strategies are examined.

Quantifying the roles of vomiting, diarrhea, and residents vs. staff in norovirus transmission in U.S. nursing home outbreaks.

The role of individual case characteristics, such as symptoms or demographics, in norovirus transmissibility is poorly understood. Six nursing home norovirus outbreaks occurring in South Carolina, U.S. from 2014 to 2016 were examined. We aimed to quantify the contribution of symptoms and other case characteristics in norovirus transmission using the reproduction number (REi) as an estimate of individual case infectivity and to examine how transmission changes over the course of an outbreak. Individual estimates of REi were calculated using a maximum likelihood procedure to infer the average number of secondary cases generated by each case. The associations between case characteristics and REi were estimated using a weighted multivariate mixed linear model. Outbreaks began with one to three index case(s) with large estimated REi's (range: 1.48 to 8.70) relative to subsequent cases. Of the 209 cases, 155 (75%) vomited, 164 (79%) had diarrhea, and 158 (76%) were nursing home residents (vs. staff). Cases who vomited infected 2.12 (95% CI: 1.68, 2.68) times the number of individuals as non-vomiters, cases with diarrhea infected 1.39 (95% CI: 1.03, 1.87) times the number of individuals as cases without diarrhea, and resident-cases infected 1.53 (95% CI: 1.15, 2.02) times the number of individuals as staff-cases. Index cases tended to be residents (vs. staff) who vomited and infected considerably more secondary cases compared to non-index cases. Results suggest that individuals, particularly residents, who vomit are more infectious and tend to drive norovirus transmission in U.S. nursing home norovirus outbreaks. While diarrhea also plays a role in norovirus transmission, it is to a lesser degree than vomiting in these settings. Results lend support for prevention and control measures that focus on cases who vomit, particularly if those cases are residents.

Norovirus Outbreak Surveillance, China, 2016-2018.

CaliciNet China, a network of provincial, county, and city laboratories coordinated by the Chinese Centers for Disease Control and Prevention, was launched in October 2016 to monitor the epidemiology and genotype distribution of norovirus outbreaks in China. During October 2016–September 2018, a total of 556 norovirus outbreaks were reported, and positive fecal samples from 470 (84.5%) outbreaks were genotyped. Most of these outbreaks were associated with person-to-person transmission (95.1%), occurred in childcare centers or schools (78.2%), and were reported during November–March of each year (63.5%). During the 2-year study period, 81.2% of all norovirus outbreaks were typed as GII.2[P16]. In China, most norovirus outbreaks are reported by childcare centers or schools; GII.2[P16] is the predominant genotype. Ongoing surveillance by CaliciNet China will provide information about the evolving norovirus genotype distribution and outbreak characteristics important for the development of effective interventions, including vaccines.

Survival of a norovirus surrogate on surfaces in synthetic gastric fluid

Norovirus (NoV) can survive in buffer at a range of pH values. However, when variations to pH are combined with the enzymatic conditions typical in gastric fluid, NoV survival is less predictable. Added to this, the material on which expelled vomitus fluid lands e.g. safety vinyl or carpet, might also affect the level of NoV survival in the environment. This study assessed survival of the NoV surrogate Feline calicivirus (FCV) after application onto four material types in the presence of synthetic gastric fluid of varying pH values. Synthetic gastric fluid of varying pH values (1.5, 2.5, 3.5 and 4.5) containing FCV (1×106 PFU/100 μL of gastric fluid) was seeded (100 μL) onto four material types: Formica, safety vinyl, cotton sheet and carpet tiles (2 cm × 2 cm) and left for 0, 30 and 60 minutes before recovering and identifying any viable viruses via plaque assay. FCV survived in synthetic gastric fluid at pH values as low as 2.5 and in some cases as low as 1.5 for at least 30 min when associated with certain materials. Greater average numbers of viable virus were recovered from the more absorbent materials of cotton (1900 PFU/sample) and carpet (1600 PFU/sample) compared with Formica (360 PFU/sample) and safety vinyl (380 PFU/sample). This study showed that FCV can survive in synthetic gastric fluids of low pH values for significant time periods especially on absorbent materials. This emphasises the importance of ensuring effective cleaning and decontamination procedures, particularly of soft furnishings and laundry, for infection prevention and control of NoV outbreaks.

Identification of a norovirus outbreak on a hematopoietic stem cell transplant unit and development and implementation of a novel infection prevention algorithm for controlling transmission.

Controlling norovirus transmission in units with immunocompromised patients is challenging. We present a cluster of norovirus cases that occurred on a stem-cell transplant unit and the prevention efforts that were implemented to limit the outbreak. Protocols developed to control this cluster may provide a model for other facilities.

Norovirus detection in environmental samples in norovirus outbreaks in closed and semi-closed settings

Environmental surfaces are a potential vehicle for the transmission of norovirus outbreaks in closed and semi-closed settings. Testing of environmental samples may help control outbreaks. To assess the level of environmental contamination by norovirus in acute gastroenteritis outbreaks in closed or semi-closed settings (nursing homes, schools, kindergartens, youth accommodations, hospitals and social health centres) in the Barcelona region between January 2017 and March 2019. A prospective surveillance study was carried out. Environmental samples (529) were collected in 46 of the 50 outbreaks of acute norovirus gastroenteritis from environmental surfaces of common areas, bathrooms and kitchens in closed and semi-closed settings when the outbreak was notified and 10 days later. Instructions for taking environmental samples were distributed to public health inspectors. Norovirus was detected by reverse transcription polymerase chain reaction. Environmental samples were positive for norovirus in 31 (67.4%) outbreaks. Norovirus was most frequently detected on elevator buttons (4/17, 24%), toilet handles (16/66, 24%) and handrail bars (7/34, 21%). Positive samples from the first sampling were mainly found in bathrooms and greater viral persistence in the second sampling was found on elevator buttons and TV remote controls. Nursing homes were the setting with the most types of environmental surfaces contaminated (82% in first samples and 55% in second samples). The probability of virus detection is independent of the time between notification of the outbreak or symptom onset and sample collection. Our results suggest possible defects in cleaning protocols and disinfection in closed and semi-closed settings.

Brote de gastroenteritis causado por norovirus en un hotel de Menorca, España

ObjectivesTo establish the agent responsible for a gastroenteritis outbreak in a hotel in Menorca (Spain) in September 2016. MethodsThe study included epidemiological and laboratory analysis. Environmental and stool samples were examined for bacterial and viral pathogens. ResultsOne hundred and fifty-one cases were detected, 123 among the tourists staying in the hotel and 28 affecting the staff. The presence of genotypeII norovirus was discovered in the microbiological studies of patient's faeces, as well as in the surface samples of rooms and common areas. The control plan implemented allowed for control of the outbreak. ConclusionsThis study on a genotypeII norovirus outbreak reveals the importance of a rapid response for controlling these types of outbreaks.

Norovirus outbreak in a natural playground: A One Health approach.

Norovirus constitutes the most frequently identified infectious cause of disease outbreaks associated with untreated recreational water. When investigating outbreaks related to surface water, a One Health approach is insightful. Historically, there has been a focus on potential contamination of recreational water by bird droppings and a recent publication demonstrating human noroviruses in bird faeces suggested this should be investigated in future water‐related norovirus outbreaks. Here, we describe a One Health approach investigating a norovirus outbreak in a natural playground. On social media, a large amount of waterfowl were reported to defecate near these playground premises leading to speculations about their potential involvement. Surface water, as well as human and bird faecal specimens, was tested for human noroviruses. Norovirus was found to be the most likely cause of the outbreak but there was no evidence for transmission via waterfowl. Cases had become known on social media prior to notification to the public health service underscoring the potential of online media as an early warning system. In view of known risk factors, advice was given for future outbreak investigations and natural playground design.

An agent-based model about the effects of fake news on a norovirus outbreak

BackgroundConcern about health misinformation is longstanding, especially on the Internet. MethodsUsing agent-based models, we considered the effects of such misinformation on a norovirus outbreak, and some methods for countering the possible impacts of “good” and “bad” health advice. The work explicitly models spread of physical disease and information (both online and offline) as two separate but interacting processes. The models have multiple stochastic elements; repeat model runs were made to identify parameter values that most consistently produced the desired target baseline scenario. Next, parameters were found that most consistently led to a scenario when outbreak severity was clearly made worse by circulating poor quality disease prevention advice. Strategies to counter “fake” health news were tested. ResultsReducing bad advice to 30% of total information or making at least 30% of people fully resistant to believing in and sharing bad health advice were effective thresholds to counteract the negative impacts of bad advice during a norovirus outbreak. ConclusionHow feasible it is to achieve these targets within communication networks (online and offline) should be explored.

Molecular epidemiology of norovirus outbreaks in Argentina, 2013-2018.

Noroviruses are a leading cause of endemic and epidemic acute gastroenteritis in all age groups. However, in Latin America, there are limited and updated data regarding circulating genotypes. The aim of this study was to assess the prevalence and genetic diversity of norovirus outbreaks in Argentina from 2013 to 2018. Stool samples from 29 acute gastroenteritis (AGE) outbreaks were available for viral testing. Norovirus was detected in samples from 18 (62.1%) outbreaks (2 GI and 16 GII). Both GI outbreaks were typed as GI.6[P11] whereas 10 different GII genotypes were detected, in which GII.4 viruses were the most frequently detected (29.4%, associated with GII.P31 and GII.P16) followed by GII.1[P33] and GII.6[P7] (17.6% each). Like GII.4 viruses, GII.2 viruses were also detected in association with different polymerases (GII.P2 and GII.P16). Our findings underscore the importance of dual RNA-dependent RNA polymerase-VP1 typing since recombinant strains with new polymerase sequences emerge frequently suggesting a possible role in improved fitness of these viruses. This study represents the most recent multi-year assessment of the molecular epidemiology of norovirus strains associated with AGE outbreaks in Argentina. Molecular surveillance of norovirus has to be considered to monitor possible changes in dominant genotypes which may assist to inform the formulation of future vaccines.

Nosocomial Norovirus Outbreak Associated with Persistent Norovirus Excretion in a Patient Receiving Corticosteroid Therapy

Nosocomial Norovirus Outbreak Associated with Persistent Norovirus Excretion in a Patient Receiving Corticosteroid Therapy

On Statistical Underreporting of Norovirus-Infections: Insights from Register Data of Two Local Public Health Authorities

Only laboratory-confirmed norovirus (NoV) cases have to be notified to the Robert Koch Institute (RKI) since 2011, but not other, e. g. clinical-epidemiological cases. It can be assumed that the extent of underreporting of NoV cases in Germany has significantly increased since then. To discuss the extent of underreporting, we wanted to find out how many laboratory tests were carried out during gastroenteritis outbreaks. Furthermore, the significance of NoV outbreaks in occupational health is discussed. Of all pseudonymized gastroenteritis outbreak data reported to 2 local health authorities between 2011 and 2015, the proportion of NoV outbreaks and reported cases of infection among employees in hospitals and community facilities (nursing homes for the elderly, day-care centers, schools) confirmed by laboratory tests was calculated retrospectively. Only a few gastroenteritis outbreaks in day-care centers were etiologically diagnosed, so that only 6% and less could be classified as NoV outbreaks. In nursing homes for the elderly, about half of the outbreaks were classified as NoV, in hospitals almost all of them. Employees accounted for up to 23% of those affected in NoV outbreaks. The low level of laboratory diagnostics carried out during gastroenteritis outbreaks in day-care centers suggests a considerable number of hidden NoV cases. The significant proportion of staff relative to the total number of infected persons during the outbreaks highlights the importance of the burden of NoV outbreaks as a topic in occupational health. Further, large-scale prospective studies are needed to empirically substantiate these initial findings.

Humoral and Mucosal Immune Responses to Human Norovirus in the Elderly.

Most information on mucosal and systemic immune response to norovirus infection is derived from human challenge studies, birth cohort studies, or vaccine trials in healthy adults. However, few data are available on immune responses to norovirus in the elderly. To study the mucosal and systemic immune response against norovirus, 43 long-term care facilities were enrolled prospectively in 2010-2014. Baseline saliva samples from 17 facilities, cases and controls up to day 84 from 10 outbreaks, as well as acute and convalescent sera were collected. Norovirus-specific immunoglobulin A (IgA) levels in baseline saliva samples were low and increased in both symptomatic patients and asymptomatic shedders at day 5 after onset during outbreaks. Receiver operating characteristics analysis correctly assigned prior norovirus infection in 23 (92%) of 25 participants. Cases and asymptomatic shedders showed seroconversion for IgG (80%), IgA (78%), and blockade antibodies (87%). Salivary IgA levels strongly correlated with increased convalescent serum IgA titers and blockade antibodies. Salivary IgA levels strongly correlated with serum IgA titers and blockade antibodies and remained elevated 3 months after a norovirus outbreak. A single salivary sample collected on day 14 could be used to identify recent infection in a suspected outbreak or to monitor population salivary IgA.

Efficient management of a norovirus outbreak causing gastroenteritis in two hotels in Spain, 2014

ObjectivesTo determine the aetiological agent causing a gastroenteritis outbreak in two hotels in Majorca (Spain) on August and September 2014. MethodsAn epidemiological study was carried out. Environmental and stool samples were analyzed for different pathogens, including norovirus. ResultsEpidemiological analysis detected 79 cases among the tourists hosted in the affected hotels over the period 18th August to 3rd September. They included 52 (attack rate: 6.4%) and 27 (attack rate: 3.0%) cases in hotel A and B, respectively. Seven of the staff members were also affected. Microbiological analyses detected genotype 2 norovirus in patient's stool samples, in rooms and in common areas’ surfaces. The specific control plan rapidly implemented at the beginning of the outbreak, and further adapted for norovirus elimination, allowed to control the outbreak. ConclusionsOur study demonstrates that the outbreak was caused by genotype 2 norovirus, and reflects the importance of a rapid analysis and response for its control.

Population-Level Human Secretor Status Is Associated With Genogroup 2 Type 4 Norovirus Predominance.

Noroviruses are a leading cause of acute gastroenteritis. Genogroup 2 type 4 (GII.4) has been the dominant norovirus genotype worldwide since its emergence in the mid-1990s. Individuals with a functional fucosyltransferase-2 gene, known as secretors, have increased susceptibility to GII.4 noroviruses. We hypothesized that this individual-level trait may drive GII.4 norovirus predominance at the human population level. We conducted a systematic review for studies reporting norovirus outbreak or sporadic case genotypes and merged this with data on proportions of human secretor status in various countries from a separate systematic review. We used inverse variance-weighted linear regression to estimate magnitude of the population secretor-GII.4 proportion association. Two hundred nineteen genotype and 112 secretor studies with data from 38 countries were included in the analysis. Study-level GII.4 proportion among all noroviruses ranged from 0% to 100%. Country secretor proportion ranged from 43.8% to 93.9%. We observed a 0.69% (95% confidence interval, 0.19-1.18) increase in GII.4 proportion for each percentage increase in human secretor proportion, controlling for Human Development Index. Norovirus evolution and diversity may be driven by local population human host genetics. Our results may have vaccine development implications including whether specific antigenic formulations would be required for different populations.

Absence of norovirus contamination in shellfish harvested and commercialized in the Northeast coast of Brazil.

Norovirus (NoV) is the main cause of gastroenteritis outbreaks worldwide. Although NoV spreads mainly from person to person, it is estimated that a large proportion of NoV outbreaks are caused by foodborne transmission. Bivalve mollusks are one of the most important foods involved in NoV transmission to humans. Little is known about NoV prevalence in shellfish harvested and commercialized in Brazil. The aim of this study was to map, for the first time, the distribution of NoV contamination in oysters and mussels harvested and commercialized in the coast of Pernambuco state, northeast Brazil. A total of 380 mollusks (260 oysters and 120 mussels) were collected between February and August 2017 either directly from harvesting areas or obtained from beach vendors at 17 sites in Pernambuco. Samples were processed and tested for NoV contamination using a SYBR Green real-time PCR assay. All samples were negative for NoV GI or GII contamination, suggesting a low risk of NoV contamination from this food source during the study period. Additional surveys in different areas of the Brazilian coast are warranted to monitor the risk of NoV infection upon seafood consumption.

What proportion of care home outbreaks are caused by norovirus? An analysis of viral causes of gastroenteritis outbreaks in care homes, North East England, 2016\u20132018

BackgroundOutbreaks of infectious gastroenteritis are common in care homes for the elderly. Norovirus can cause these outbreaks, but diagnosis is frequently based solely on clinical characteristics. Our objective in this study was to describe the epidemiology of norovirus and other gastrointestinal pathogens in these settings.MethodsWe analysed surveillance data from gastroenteritis outbreaks reported in North East England between 04 July 2016 to 01 July 2018. Stool samples taken during these outbreaks were tested for a range of viral and bacterial pathogens. We described the epidemiology of these outbreaks and explored the characteristics of norovirus outbreaks versus from other viral causes using multivariable logistic regression.ResultsFrom the 566 care home gastroenteritis outbreaks in this study, we found that norovirus was the pathogen most frequently isolated. Norovirus was detected in 64% of outbreaks with a pathogen identified. Sapovirus was found in 13%; rotavirus in 11%. We found that norovirus outbreaks were associated with higher attack rates (aOR 1.03, 95% CI 1.01–1.05) and fewer cases sampled (aOR 0.74, 95% CI 0.60–0.91), compared to outbreaks caused by other viral pathogens.ConclusionsThese results are important as they quantify the contribution of norovirus to gastroenteritis outbreaks in care homes. Given this evidence, we emphasize the importance of non-specific outbreak interventions that can affect the impact of all such outbreaks. We further recommend that these findings are used to inform the implementation strategies of any norovirus-specific interventions such as a norovirus vaccine.

Analysis on the duration of intestinal detoxification in restaurant employee infected with Norovirus during the outbreak

Objective: To explore the duration of intestinal detoxification and its related factors infected with Norovirus, and to provide scientific evidences for the prevention and control of acute gastroenteritis caused by Norovirus in the future. Methods: Follow up and sampling program on 115 employees in a restaurant outbreak of Norovirus in Chengdu in 2017 was carried out. Anal swab was collected every 3 d or 7 d for nucleic acid detection, and the experimental results were statistically analyzed. Results: The positive rates of Norovirus in restaurant employee were 14.78%, 7.89%, 3.51% and 0.88% on the 7(th), 11(th), 17(th) and 24(th) day, respectively. During the follow-up period, the positive rates of Norovirus decreased as time increased. The positive rate of all employees was up to 14.78% on the 7(th) day. The positive rates had no significant difference between different sex and between different types of work. The duration of detoxification averaged 14.94 days and the maximum of detoxification time was on 28 days. The detoxification period of treatment case was shorter than that of asymptomatic carriers. Conclusions: There were asymptomatic carriers in restaurant employees during the outbreak of Norovirus that their role as a source of infection in the transmission of Norovirus should not be neglected. In the treatment of the epidemic, we should strengthen the sampling and testing of practitioners, and strictly implement isolation measures for positive detection.