Acute Gastroenteritis Outbreak Among Colorado River Rafters and Backpackers in the Grand Canyon, 2022.

INTRODUCTION: From April 1 to May 31, 2022, Grand Canyon National Park received increased acute gastroenteritis reports. Pooled portable toilet specimens identified norovirus genogroups I and II. We sought to determine outbreak transmission contributors and individual risk factors while rafting or backpacking in the park. METHODS: Grand Canyon rafters and backpackers were surveyed online from June 13-July 8, 2022, and a Cox proportional hazards model was used to identify predictors associated with illness and adjusted for potential confounding factors. RESULTS: Among 762 surveys, 119 cases and 505 well persons submitted complete survey data. Illness among rafters was associated with interaction with ill persons during the trip (adjusted hazard ratio [adjHR] = 3.4 [95%CI 2.3-5.0]) and lack of any hand hygiene (1.2 [0.7-1.9]) or use of only sanitizer or water (1.6 [1.04-2.6]) before snacks. Younger rafters had higher illness rates compared to those ≥60 y (1.5 [1.2-1.8] for ages 40-59 and 2.2 [1.4-3.5] for ages <40 y). CONCLUSIONS: Person-to-person transmission likely accounted for the widespread outbreak. Future outbreak mitigation efforts on river trips could focus on symptom screening before the trip starts, prompt separation of ill and well passengers, strict adherence to hand hygiene with soap and water, minimizing social interactions among rafting groups, and widespread outbreak notices and education to all park users.

Experimental Study of the Mechanical Transmission of Rabbit Hemorrhagic Disease Virus (RHDV2/b) by Aedes albopictus (Diptera: Culicidae) and Phlebotomus papatasi (Diptera: Psychodidae).

Rabbit hemorrhagic disease (RHD) is caused by a lagovirus mainly affecting European rabbits (Oryctolagus cuniculus), although other European and North American lagomorph species are also susceptible to fatal infection by the new viral variant RHDV2/b. In the present work, direct mechanical transmission of the rabbit hemorrhagic disease virus (RHDV2/b variant) by the hematophagous Diptera Aedes albopictus (Skuse) (Diptera: Culicidae) and the sand fly Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) was tested. For each species, six and three laboratory rabbits were exposed to bites of dipterous females partially fed on RHDV2/b viral suspension 2 h and 24 h prior to exposure, respectively. The rabbits were then monitored for clinical changes and mortality for 35 d, and seroconversion was assessed by indirect ELISA. No rabbit died or showed clinical signs of disease, and seroconversion was recorded in two rabbits challenged with P. papatasi females fed the viral suspension 2 h prior to exposure. The number of RHDV2/b RNA copies/female was higher in Ae. albopictus than in P. papatasi but the decrease over time of RNA load in Ae. albopictus was greater than that in P. papatasi. The results of this study suggest the inability of Ae. albopictus to serve as a direct mechanical vector of RHDV2/b, but sand flies could play a role in the local transmission of RHD.

Fractal-fractional and stochastic analysis of norovirus transmission epidemic model with vaccination effects.

In this paper, we investigate an norovirus (NoV) epidemic model with stochastic perturbation and the new definition of a nonlocal fractal-fractional derivative in the Atangana-Baleanu-Caputo (ABC) sense. First we present some basic properties including equilibria and the basic reproduction number of the model. Further, we analyze that the proposed stochastic system has a unique global positive solution. Next, the sufficient conditions of the extinction and the existence of a stationary probability measure for the disease are established. Furthermore, the fractal-fractional dynamics of the proposed model under Atangana-Baleanu-Caputo (ABC) derivative of fractional order "[Formula: see text]" and fractal dimension "[Formula: see text]" have also been addressed. Besides, coupling the non-linear functional analysis with fixed point theory, the qualitative analysis of the proposed model has been performed. The numerical simulations are carried out to demonstrate the analytical results. It is believed that this study will comprehensively strengthen the theoretical basis for comprehending the dynamics of the worldwide contagious diseases.

A Waterborne Gastroenteritis Outbreak Caused by a GII Norovirus in a Holiday Camp in Catalonia (Spain), 2017.

On 2 February 2017, Epidemiological Surveillance Services were notified of an outbreak of acute gastroenteritis (AGE) among schoolchildren who had taken part of a school trip from 30 January to 3 February 2017 at a holiday camp in Catalonia. A retrospective cohort study was performed to identify the causative agent, estimate the magnitude of the outbreak and identify its source, as well as to determine the route of transmission. Data collected by standardised questionnaires identified 41 episodes of AGE among 174 individuals who attended the camp. Cases had mainly symptoms of abdominal pain (73.8%), nausea (64.3%), vomiting (54.8%), diarrhoea (45.2%) and headache (42.9%). Consumption of water was associated with gastroenteritis (crude RR: 1.72, 95%CI: 1.01-2.92; adjusted RR: 1.88, 95%CI 1.03-3.56). NoV GII was detected in faeces (5 out of 13) and water samples. Additionally, faecal indicator bacteria and protozoa were detected in water samples. The outbreak showed a high attack rate and was caused by a natural water fountain not properly treated and not monitored for safety quality. There could have been a discharge of wastewater at a point close to the fountain; however, the source of contamination of the water could not be identified. Health education may be useful to eliminate risks associated with the consumption of untreated water from natural fountains.

Noroviruses-The State of the Art, Nearly Fifty Years after Their Initial Discovery.

Human noroviruses are recognised as the major global cause of viral gastroenteritis. Here, we provide an overview of notable advances in norovirus research and provide a short recap of the novel model systems to which much of the recent progress is owed. Significant advances include an updated classification system, the description of alternative virus-like protein morphologies and capsid dynamics, and the further elucidation of the functions and roles of various viral proteins. Important milestones include new insights into cell tropism, host and microbial attachment factors and receptors, interactions with the cellular translational apparatus, and viral egress from cells. Noroviruses have been detected in previously unrecognised hosts and detection itself is facilitated by improved analytical techniques. New potential transmission routes and/or viral reservoirs have been proposed. Recent in vivo and in vitro findings have added to the understanding of host immunity in response to norovirus infection, and vaccine development has progressed to preclinical and even clinical trial testing. Ongoing development of therapeutics includes promising direct-acting small molecules and host-factor drugs.

Comparative study of the geographical spread of genogroup II porcine norovirus and human norovirus.

Livestock pigs and porcine norovirus could be candidate tools for future studies on the geographic isolation of norovirus. In this study, we provide the first evidence for geographic isolation of the host as a determinant of the distribution of subgenotypes of the porcine norovirus genogroup II (GII) genotype 11. Environmental water samples were collected from peri-urban streams and estuaries in South Korea between 2014 and 2020. In total, 488 GII region C sequences of norovirus open reading frame 2 were isolated. A total of 14 genotypes were detected, two of which (GII.11 and GII.18) corresponded to porcine norovirus. Five human norovirus genotypes (GII.2, GII.3, GII.4, GII.6, and GII.17) and one porcine norovirus genotype (GII.11) comprised the subgenotypes. Integrated analysis of seasonal and geographical factors revealed that the possibility of the co-emergence of different GII.11 subgenotypes in the same province was lower than that of human norovirus subgenotypes in the same province. Additional algorithms designed to eliminate potential biases further supported the estimated restricted geographical spread of the GII.11 subgenotypes. Fecal contamination source tracking revealed low detection rates of porcine norovirus in the absence of upstream pig farms. These results suggest that a one-sided viral transmission route, mainly dependent on indirect contact owing to the limited chance of direct contact between geographically separated livestock pig populations, may be responsible for the restricted geographical spread of the GII.11 subgenotypes.

Measuring transfer of human norovirus during sandwich production: Simulating the role of food, food handlers and the environment.

Foodborne outbreaks associated with transmission of norovirus are increasingly becoming a public health concern. Foods can be contaminated with faecal material at the point of production or during food preparation, in both the home and in commercial premises. Transmission of norovirus occurs through the faecal-oral route, either via person-to-person contact or through faecal-contamination of food, water, or environmental surfaces. Understanding the role and pathways of norovirus transmission - either via food handlers' hands, contaminated foods or the environment - remains a key public health priority to reduce the burden of norovirus-associated gastroenteritis. However the proportion of norovirus that is typically transferred remains unknown. Understanding this is necessary to estimate the risk of infection and the burden of gastroenteritis caused by norovirus. In this paper we present a novel method of capture, concentration and molecular detection of norovirus from a wider range of complex food matrices than those demonstrated in existing published methods. We demonstrate that this method can be used as a tool to detect and quantify norovirus from naturally contaminated food, and for monitoring norovirus transfer between food handlers' gloved hands, food or the environment. We measure the effect of introducing contamination at different food production process stages, to the final food product, to determine whether this could cause infection and disease. Between 5.9 and 6.3 Log10 cDNA copies/µl of norovirus GII were inoculated onto food handlers' gloved hands, food or the environment and 1.1-7.4% of norovirus contamination was recovered from all samples tested. When interpreted quantitatively, this percentage equates to levels predicted to be sufficient to cause infection and disease through consumption of the final food product, demonstrating a public health risk. Overall detection and quantification of norovirus from foods, food handlers' gloved hands and the environment, when suspected to be implicated in foodborne transmissions, is paramount for appropriate outbreak investigation.

Norovirus gastroenteritis outbreaks in military units: a systematic review.

INTRODUCTION: Norovirus gastroenteritis is one of the most frequent causes of personnel unavailability in military units, being associated with significant morbidity and degradation of their operational effectiveness. The disease is usually mild but can be severe and life-threatening in young and healthy soldiers, who are prone to dehydration due to intensive daily activity. Despite its impact, the full extent of the norovirus gastroenteritis burden in military forces remains unclear. This systematic review aims to evaluate the impact and ascertain clinical and epidemiological features of norovirus outbreaks that have occurred in the military forces. METHODS: The systematic review followed the Preferred Reporting Items for Systemic Reviews and Meta-Analysis (PRISMA) guidelines and used three databases: PubMed, Scopus, and LILACs. Papers published up to 1 September 2019 were included without restrictions if they reported one or more outbreaks in the military forces on active duty, either on national territories or deployed overseas. RESULTS: A total of 343 papers were retrieved from the literature search. After inclusion/exclusion criteria a total of 39 eligible papers were considered. From 1988 (first reported outbreak in the military) to 2018 more than 101 norovirus outbreaks have been reported in the military, accounting for at least 24 332 cases. Secondary transmission was emphasised as the main route of norovirus transmission in the military forces, with eating outside the military setting an important route for the primary cases. CONCLUSIONS: The present review highlights that norovirus gastroenteritis has been a burden to military troops both in combat and on peacekeeping operations. Norovirus disease has been shown to exact a substantial toll on mission readiness and operational effectiveness. It is noteworthy that the impact of norovirus outbreaks among military units is underestimated because the literature review retrieved information from the armed forces from only nine countries.

An outbreak of gastroenteritis associated with a novel GII.8 sapovirus variant-transmitted by vomit in Shenzhen, China, 2019.

BACKGROUND: Human Sapoviruses (SaVs) has been reported as one of the causative agents of acute gastroenteritis (AGE) worldwide. An outbreak of SaVs affected 482 primary school students during spring activities from February 24 to March 11, 2019 in Shenzhen City, China. Our study was aimed at determining the epidemiology of the outbreak, investigating its origins, and making a clear identification of the SaVs genetic diversity. METHODS: Epidemiological investigation was conducted for this AGE outbreak. Stool samples were collected for laboratory tests of causative agents. Real-time reverse-transcription polymerase chain reaction (rRT-PCR) and conventional RT-PCR were used for detecting and genotyping of SaVs. The nearly complete genome of GII.8 SaV strains were amplified and sequenced by using several primer sets designed in this study. Phylogenetic analysis was performed to characterize the genome of GII.8 SaV strains. RESULTS: The single factor analysis showed that the students who were less than 1.5 m away from the vomitus in classroom or playgroundwere susceptible (P < 0.05). Seven of 11 fecal samples from patients were positive for GII.8 SaV genotype. In this study, we obtained the genome sequence of a SaV GII.8 strain Hu/SaV/2019008Shenzhen/2019 /CHN (SZ08) and comprehensively analyzed the genetic diversity. The phylogenetic analysis showed that the GII.8 strain SZ08 formed an independent branch and became a novel variant of GII.8 genotype. Strain SZ08 harbored 11 specific amino acid variations compared with cluster A-D in full-length VP1. CONCLUSIONS: This study identified SaVs as the causative agents for the AGE outbreak. Strain Hu SZ08 was clustered as independent branch and there was no recombination occurred in this strain SZ08. Further, it might become the predominant strain in diarrhea cases in the near future. Constant surveillance is required to monitor the emerging variants which will improve our knowledge of the evolution of SaVs among humans.

Involvement of Workers in Closed and Semiclosed Institutions in Outbreaks of Acute Gastroenteritis Due to Norovirus.

Norovirus outbreaks frequently occur in closed or semiclosed institutions. Recent studies in Catalonia and various countries indicate that, during outbreaks in these institutions, norovirus is detected in between 23% and 60% of workers, and the prevalence of infection in asymptomatic workers involved in outbreaks ranges from 17% to 40%. In this work, we carried out a prospective study to investigate the involvement of workers in closed and semiclosed institutions during outbreaks. The attack rates (ARs) and the rate ratios (RRs) were calculated according to the type of transmission and occupational category. The RRs and 95% confidence intervals (CIs) between workers and users were calculated. The mean cycle of quantification (Cq) values were compared according to the genogroup and the presence of symptoms. ARs were higher in person-to-person transmission than in common vehicle outbreaks, and 38.8% of workers were symptomatic. The RR between workers and users was 0.46 (95% CI 0.41-0.52). The ARs in workers were high, particularly in workers with closer contact with users. The mean Cq was lower in patients than in asymptomatic infected persons, although the difference was only significant for genogroup I (GI). The frequency of asymptomatic infected persons suggests that personal hygiene measures should be followed by all workers in the centers affected.

Phylogenetic Investigation of Norovirus Transmission between Humans and Animals.

Norovirus infections are a leading cause of acute gastroenteritis worldwide, affecting people of all ages. There are 10 norovirus genogroups (GI-GX) that infect humans and animals in a host-specific manner. New variants and genotypes frequently emerge, and their origin is not well understood. One hypothesis is that new human infections may be seeded from an animal reservoir, as human noroviruses have occasionally been detected in animal species. The majority of these sequences were identified as older GII.4 variants, but a variety of other GIIs and GIs have been detected as well. While these sequences share at least 94% nt similarity with human strains, most of them are >98% identical to human strains. The fact that these strains were detected in animals after they had been detected through human surveillance to be already circulating in humans suggests human-to-animal transmission.

Aerosolization and recovery of viable murine norovirus in an experimental setup.

Noroviruses are the major cause for viral acute gastroenteritis in the world. Despite the existing infection prevention strategies in hospitals, the disease continues to spread and causes extensive and numerous outbreaks. Hence, there is a need to investigate the possibility of airborne transmission of norovirus. In this study, we developed an experimental setup for studies on the infectivity of aerosolized murine norovirus (MNV), a model for the human norovirus. Two aerosol generation principles were evaluated: bubble bursting, a common natural aerosolization mechanism, and nebulization, a common aerosolization technique in laboratory studies. The aerosolization setup was characterized by physical and viral dilution factors, generated aerosol particle size distributions, and the viral infectivity after aerosolization. We found a lower physical dilution factor when using the nebulization generator than with the bubble bursting generator. The viral dilution factor of the system was higher than the physical dilution; however, when comparing the physical and viral dilution factors, bubble bursting generation was more efficient. The infectivity per virus was similar using either generation principle, suggesting that the generation itself had a minor impact on MNV infectivity and that instead, the effect of drying in air could be a major reason for infectivity losses.

Interaction between norovirus and Histo-Blood Group Antigens: A key to understanding virus transmission and inactivation through treatments?

Human noroviruses (HuNoVs) are a main cause of acute gastroenteritis worldwide. They are frequently involved in foodborne and waterborne outbreaks. Environmental transmission of the virus depends on two main factors: the ability of viral particles to remain infectious and their adhesion capacity onto different surfaces. Until recently, adhesion of viral particles to food matrices was mainly investigated by considering non-specific interactions (e.g. electrostatic, hydrophobic) and there was only limited information about infectious HuNoVs because of the absence of a reliable in vitro HuNoV cultivation system. Many HuNoV strains have now been described as having specific binding interactions with human Histo-Blood Group Antigens (HBGAs) and non-HBGA ligands found in food and the environment. Relevant approaches to the in vitro replication of HuNoVs were also proposed recently. On the basis of the available literature data, this review discusses the opportunities to use this new knowledge to obtain a better understanding of HuNoV transmission to human populations and better evaluate the hazard posed by HuNoVs in foodstuffs and the environment.

Differences in epidemic spread patterns of norovirus and influenza seasons of Germany: an application of optical flow analysis in epidemiology.

This analysis presents data from a new perspective offering key insights into the spread patterns of norovirus and influenza epidemic events. We utilize optic flow analysis to gain an informed overview of a wealth of statistical epidemiological data and identify trends in movement of influenza waves throughout Germany on the NUTS 3 level (413 locations) which maps municipalities on European level. We show that Influenza and norovirus seasonal outbreak events have a highly distinct pattern. We investigate the quantitative statistical properties of the epidemic patterns and find a shifted distribution in the time between influenza and norovirus seasonal peaks of reported infections over one decade. These findings align with key biological features of both pathogens as shown in the course of this analysis.

Sapovirus: an emerging cause of childhood diarrhea.

PURPOSE OF REVIEW: Sapovirus, a genus in the Caliciviridae family alongside norovirus, is increasingly recognized as an important cause of childhood diarrhea. Some challenges exist in our ability to better understand sapovirus infections, including the inability to grow sapovirus in cell culture, which has hindered diagnosis and studies of immunity. Another challenge is that individuals with sapovirus infection are commonly coinfected with other enteric pathogens, complicating our ability to attribute the diarrhea episode to a single pathogen. RECENT FINDINGS: Development of molecular methods for sapovirus detection has increased our ability to measure disease prevalence. The prevalence of sapovirus varies between 1 and 17% of diarrhea episodes worldwide, with the highest burden in young children and older adults. Further, epidemiological studies have used novel approaches to account for the presence of coinfections with other enteric pathogens; one multisite cohort study of children under two years of age found that sapovirus had the second-highest attributable incidence among all diarrheal pathogens studied. SUMMARY: Especially in settings where rotavirus vaccines have been introduced, efforts to reduce the overall burden of childhood diarrhea should focus on the reduction of sapovirus transmission and disease burden.

Exosome-mediated human norovirus infection.

Human norovirus (HuNoV) is a leading cause of acute gastroenteritis. Outbreaks normally occur via the fecal-oral route. HuNoV infection is thought to occur by viral particle transmission, but increasing evidence suggests a function for exosomes in HuNoV infection. HuNoV is contained within stool-derived exosomes, and exosome-associated HuNoV has been shown to replicate in human intestinal enteroids. In this study, we examine exosome-associated HuNoV infection of Vero cells and show that exosomes containing HuNoV may attach, infect, and be passaged in Vero cells. These findings support earlier findings and have implications for developing HuNoV disease intervention strategies.

Norovirus transmission mediated by asymptomatic family members in households.

The transmission of human norovirus excreted from infected persons occasionally causes sporadic infections and outbreaks. Both symptomatic patients and asymptomatic carriers have been reported to contribute to norovirus transmission, but little is known about the magnitude of the contribution of asymptomatic carriers. We carried out a 1-year survey of residents of a district of Bangkok, Thailand to determine the percentage of norovirus transmissions originating from asymptomatic individuals. We screened 38 individuals recruited from 16 families from May 2018 to April 2019 for GI and GII genotypes. Norovirus was detected every month, and 101 of 716 stool samples (14.1%) from individuals with no symptoms of acute gastroenteritis were norovirus-positive. The average infection frequency was 2.4 times per person per year. Fourteen genotypes were identified from the positive samples, with GII.4 being detected most frequently. Notably, 89.1% of the norovirus-positive samples were provided by individuals with no diarrhea episode. Similar to cases of symptomatic infections in Thailand, asymptomatic infections were observed most frequently in December. We detected 4 cases of NV infection caused by household transmission, and 3 of the 4 transmissions originated from asymptomatic individuals. We also identified a case in which norovirus derived from an asymptomatic individual caused diarrhea in a family member. These results suggest that asymptomatic individuals play a substantial role in both the maintenance and spreading of norovirus in a community through household transmission.

Infectious Norovirus Is Chronically Shed by Immunocompromised Pediatric Hosts.

Noroviruses are a leading cause of gastroenteritis worldwide. Although infections in healthy individuals are self-resolving, immunocompromised individuals are at risk for chronic disease and severe complications. Chronic norovirus infections in immunocompromised hosts are often characterized by long-term virus shedding, but it is unclear whether this shed virus remains infectious. We investigated the prevalence, genetic heterogeneity, and temporal aspects of norovirus infections in 1140 patients treated during a 6-year period at a pediatric research hospital. Additionally, we identified 20 patients with chronic infections lasting 37 to >418 days. Using a new human norovirus in vitro assay, we confirmed the continuous shedding of infectious virus for the first time. Shedding lasted longer in male patients and those with diarrheal symptoms. Prolonged shedding of infectious norovirus in immunocompromised hosts can potentially increase the likelihood of transmission, highlighting the importance of isolation precautions to prevent nosocomial infections.