BACKGROUND: Noroviruses are the leading cause of acute gastroenteritis worldwide with GII.4 Sydney viruses responsible for the majority of infections until 2023. METHODS: To study the evolutionary dynamics of GII.4 noroviruses in the US (2011-2023), we sequenced and analyzed 406 VP1 and 335 RdRp sequences submitted to CaliciNet. RESULTS: Time-scale analysis showed the average evolutionary rate of GII.4 strains was 5.56 x 10-3 substitutions/site/year and the emergence of a new cluster within GII.4 Sydney every 4 years starting with GII.4 Sydney[P31] from 2011-2015 followed by GII.4 Sydney[P16] from 2016-2020, and the most recent GII.4 Sydney[P16]-2020 from 2021-to date. Since 2017, based on amino acids in VP1, we observed the emergence of three novel GII.4 clusters (GII.4 San Francisco, GII.4 Allegany and GII.4 Wichita). GII.4 Sydney was identified with 4 P-types (P4, P12, P16, and P31). GII.4 San Francisco and GII.4 Allegany had a P31 RdRp, whereas GII.4 Wichita strains had P4. GII.4 Allegany and GII.4 Wichita exhibited major amino acid substitutions in epitopes A-E, G, and H, while GII.4 San Francisco viruses have an alanine insertion in epitope A. Both GII.4 Allegany and GII.4 Wichita VLPs bound porcine gastric mucin at a similar level as GII.4 New Orleans and GII.4 Sydney. However, blocking of binding to VLPs by human serum pools demonstrated their antigenicity was significantly different. CONCLUSION: We identified three new emerging GII.4 noroviruses co-circulating with GII.4 Sydney. Early detection of new strains will aid in tracking their spread and assessing their pandemic potential.

BACKGROUND: Most U.S. acute gastroenteritis (AGE) episodes in children are attributed to norovirus, whereas very little information is available on adenovirus 40/41 (AdV40/41), astrovirus or sapovirus. The New Vaccine Surveillance Network (NVSN) conducted prospective, active, population-based AGE surveillance in young children. METHODS: We tested and typed stool specimens collected between December 2011 to June 2016 from one NVSN site in Kansas City for the three viruses, and calculated hospitalization and emergency department (ED) detection rate. RESULTS: Of 3,205 collected specimens, 2,453 (76.5%) were from AGE patients (339 inpatients and 2,114 ED patients) and 752 (23.5%) were from healthy controls (HC). In AGE patients, astrovirus was detected in 94 (3.8%), sapovirus in 252 (10.3%) and AdV40/41 in 101 (4.5%) of 2249 patients. In HC, astrovirus was detected in 13 (1.7%) and sapovirus in 15 (2.0%) specimens. Astrovirus type 1 (37.7%) and genogroup I sapoviruses (59.3%) were most prevalent.Hospitalization rates were 5 (AdV40/41), 4 (astrovirus) and 8 (sapovirus) per 100,000 children <11 years old, whereas ED rates were 2.4 (AdV40/41), 1.9 (astrovirus) and 5.3 (sapovirus) per 1000 children <5 years old. CONCLUSIONS: Overall, AdV40/41, astrovirus, and sapovirus were detected in 18.6% of AGE in a large pediatric hospital in Kansas City.

We detected a novel GII.4 variant with an amino acid insertion at the start of epitope A in viral protein 1 of noroviruses from the United States, Gabon, South Africa, and the United Kingdom collected during 2017-2022. Early identification of GII.4 variants is crucial for assessing pandemic potential and informing vaccine development.

BACKGROUND: Adenovirus is a known cause of hepatitis in immunocompromised children, but not in immunocompetent children. In April, 2022, following multiple reports of hepatitis of unknown aetiology and adenovirus viraemia in immunocompetent children in the USA and UK, the US Centers for Disease Control and Prevention (CDC) and jurisdictional health departments initiated national surveillance of paediatric acute hepatitis of unknown aetiology. We aimed to describe the clinical and epidemiological characteristics of children identified with hepatitis of unknown aetiology between Oct 1, 2021, and Sept 30, 2022, in the USA and to compare characteristics of those who tested positive for adenovirus with those who tested negative. METHODS: In this national surveillance investigation in the USA, children were identified for investigation if they were younger than 10 years with elevated liver transaminases (>500 U/L) who had an unknown cause for their hepatitis and onset on or after Oct 1, 2021. We reviewed medical chart abstractions, which included data on demographics, underlying health conditions, signs and symptoms of illness, laboratory results, vaccination history, radiological and liver pathology findings, diagnoses and treatment received, and outcomes. Caregiver interviews were done to obtain information on symptoms and health-care utilisation for the hepatitis illness, medical history, illness in close contacts or at school or daycare, diet, travel, and other potential exposures. Blood, stool, respiratory, and tissue specimens were evaluated according to clinician discretion and available specimens were submitted to CDC for additional laboratory testing or pathology evaluation. FINDINGS: Surveillance identified 377 patients from 45 US jurisdictions with hepatitis of unknown aetiology with onset from Oct 1, 2021, to Sept 30, 2022. The median age of patients was 2·8 years (IQR 1·2-5·0) and 192 (51%) were male, 184 (49%) were female, and one patient had sex unknown. Only 22 (6%) patients had a notable predisposing underlying condition. 347 patients (92%) were admitted to hospital, 21 (6%) subsequently received a liver transplant, and nine (2%) died. Among the 318 patients without notable underlying conditions, 275 were tested for adenovirus. Of these 116 (42%) had at least one positive specimen, and species F type 41 was the most frequent type identified (19 [73%] of 26 typed specimens were HAdV-41). Proportions of patients who had acute liver failure, received a liver transplant, and died were similar between those who tested positive for adenovirus compared with those who tested negative. Adenovirus species F was detected by polymerase chain reaction in nine pathology liver evaluations, but not by immunohistochemistry in seven of the nine with adequate liver tissue available. Interviews with caregivers yielded no common exposures. INTERPRETATION: Adenovirus, alone or in combination with other factors, might play a potential role in acute hepatitis among immunocompetent children identified in this investigation, but the pathophysiologic mechanism of liver injury is unclear. To inform both prevention and intervention measures, more research is warranted to determine if and how adenovirus might contribute to hepatitis risk and the potential roles of other pathogens and host factors. FUNDING: None.

Noroviruses are associated with one fifth of diarrheal illnesses globally and are not yet preventable with vaccines. Little is known about the effects of norovirus infection on infant gut microbiome health, which has a demonstrated role in protecting hosts from pathogens and a possible role in oral vaccine performance. In this study, we characterized infant gut microbiome changes occurring with norovirus-associated acute gastroenteritis (AGE) and the extent of recovery. Metage-nomic sequencing was performed on the stools of five infants participating in a longitudinal birth cohort study conducted in León, Nicaragua. Taxonomic and functional diversities of gut micro-biomes were profiled at time points before, during, and after norovirus infection. Initially, the gut microbiomes resembled those of breastfeeding infants, rich in probiotic species. When disturbed by AGE, Gammaproteobacteria dominated, particularly Pseudomonas species. Alpha diversity in-creased but the genes involved in carbohydrate metabolism and glycan biosynthesis decreased. After the symptoms subsided, the gut microbiomes rebounded with their taxonomic and functional communities resembling those of the pre-infection microbiomes. In this study, during disruptive norovirus-associated AGE, the gut microbiome was temporarily altered, returning to a pre-infection composition a median of 58 days later. Our study provides new insights for developing probiotic treatments and furthering our understanding of the role that episodes of AGE have in shaping the infant gut microbiome, their long-term outcomes, and implications for oral vaccine effectiveness. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

BACKGROUND: Norovirus and C. difficile are associated with diarrheal illnesses and deaths in long-term care (LTC) facilities and can be transmitted by contaminated environmental surfaces. Hygienic monitoring tools such as adenosine triphosphate (ATP) bioluminescence and indicators of fecal contamination can help to identify LTC facility surfaces with cleaning deficiencies. METHODS: High-touch surfaces in 11 LTC facilities were swabbed and tested for contamination by norovirus, a fecal indicator virus, crAssphage, and ATP which detects organic debris. High levels of contamination were defined as log ATP relative light unit values or crAssphage log genomic copy values in the 75th percentile of values obtained from each facility. RESULTS: Over 90% of surfaces tested positive for crAssphage or gave failing ATP scores. Norovirus contamination was not detected. Handrails, equipment controls, and patient beds were 4 times more likely than other surfaces or locations to have high levels of crAssphage. Patient bed handrails and tables and chairs in patient lounges had high levels of both ATP and crAssphage. CONCLUSIONS: Surfaces with high levels of ATP and crAssphage were identified. Quantifying levels of contamination longitudinally and before and after cleaning might enhance infection prevention and control procedures for reducing diarrheal illnesses in LTC facilities.

Noroviruses are a leading cause of acute gastroenteritis (AGE) among adults and children worldwide. NoroSurv is a global network for norovirus strain surveillance among children <5 years of age with AGE. Participants in 16 countries across 6 continents used standardized protocols for dual typing (genotype and polymerase type) and uploaded 1,325 dual-typed sequences to the NoroSurv web portal during 2016-2020. More than 50% of submitted sequences were GII.4 Sydney[P16] or GII.4 Sydney[P31] strains. Other common strains included GII.2[P16], GII.3[P12], GII.6[P7], and GI.3[P3] viruses. In total, 22 genotypes and 36 dual types, including GII.3 and GII.20 viruses with rarely reported polymerase types, were detected, reflecting high strain diversity. Surveillance data captured in NoroSurv enables the monitoring of trends in norovirus strains associated childhood AGE throughout the world on a near real-time basis.

BACKGROUND: The family Caliciviridae consists of a genetically diverse group of RNA viruses that infect a wide range of host species including noroviruses and sapoviruses which cause acute gastroenteritis in humans. Typing of these viruses relies on sequence-based approaches, and therefore there is a need for rapid and accurate web-based typing tools. OBJECTIVE: To develop and evaluate a web-based tool for rapid and accurate genotyping of noroviruses and sapoviruses. METHODS: The Human Calicivirus Typing (HuCaT) tool uses a set of curated reference sequences that are compared to query sequences using a k-mer (DNA substring) based algorithm. Outputs include alignments and phylogenetic trees of the 12 top matching reference sequences for each query. RESULTS: The HuCaT tool was validated with a set of 1310 norovirus and 239 sapovirus sequences covering all known human norovirus and sapovirus genotypes. HuCaT tool assigned genotypes to all queries with 100 % accuracy and was much faster (17 s) than BLAST (150 s) or phylogenetic analyses approaches. CONCLUSIONS: The web-based HuCaT tool supports rapid and accurate genotyping of human noroviruses and sapoviruses.

Noroviruses evolve by antigenic drift and recombination, which occurs most frequently at the junction between the non-structural and structural protein coding genomic regions. In 2015, a novel GII.P16-GII.4 Sydney recombinant strain emerged, replacing the predominance of GII.Pe-GII.4 Sydney among US outbreaks. Distinct from GII.P16 polymerases detected since 2010, this novel GII.P16 was subsequently detected among GII.1, GII.2, GII.3, GII.10 and GII.12 viruses, prompting an investigation on the unique characteristics of these viruses. Norovirus positive samples (n = 1807) were dual-typed, of which a subset (n = 124) was sequenced to yield near-complete genomes. CaliciNet and National Outbreak Reporting System (NORS) records were matched to link outbreak characteristics and case outcomes to molecular data and GenBank was mined for contextualization. Recombination with the novel GII.P16 polymerase extended GII.4 Sydney predominance and increased the number of GII.2 outbreaks in the US. Introduction of the novel GII.P16 noroviruses occurred without unique amino acid changes in VP1, more severe case outcomes, or differences in affected population. However, unique changes were found among NS1/2, NS4 and VP2 proteins, which have immune antagonistic functions, and the RdRp. Multiple polymerase-capsid combinations were detected among GII viruses including 11 involving GII.P16. Molecular surveillance of protein sequences from norovirus genomes can inform the functional importance of amino acid changes in emerging recombinant viruses and aid in vaccine and antiviral formulation.

Noroviruses are recognized as the leading cause of acute gastroenteritis globally. With improved molecular diagnostics developed over the last two decades, archived clinical specimens are increasingly used to investigate the historic prevalence and molecular epidemiology of human norovirus. Yet the impact of long-term storage on viral integrity in clinical specimens has not been evaluated. In this study, we retested 994 stool specimens collected between 1996 and 2017 that originally tested norovirus-positive to quantify the loss of norovirus RT-PCR positivity with increasing sample storage time at 4 degrees C. In all, 79% of samples tested positive after retesting, but there was an approximate 3% decline in the positivity ratio and 4% decline in the percentage of samples that could be genotyped with each additional year of sample storage. For samples that were originally quantified by real-time RT-PCR (collected between 2003-2017), there was an estimated 1-log loss of viral titer occurring every 7 years of sample storage. Few samples contained PCR inhibitors, assessed using a MS2 extraction control, indicating that loss of RT-PCR signal was due primarily to loss of viral RNA integrity after long-term storage of stool samples at 4 degrees C. Our results indicate that norovirus positive stool samples can be stored with minimal loss in RT-PCR positivity when stored less than a decade. Longer periods of storage may impair norovirus detection, potentially impacting historic estimates of norovirus prevalence and molecular epidemiology if derived by testing archival clinical specimens.

Globally, noroviruses are among the foremost causes of acute diarrheal disease, yet there are many unanswered questions on norovirus immunity, particularly following natural infection in young children during the first 2 years of life when the disease burden is highest. We conducted a literature review on birth cohort studies assessing norovirus infections in children from birth to early childhood. Data on infection, immunity, and risk factors are summarized from 10 community-based birth cohort studies conducted in low- and middle-income countries. Up to 90% of children experienced atleast one norovirus infection and up to 70% experienced norovirus-associated diarrhea, most often affecting children 6 months of age and older. Data from these studies help to fill critical knowledge gaps for vaccine development, yet study design and methodological differences limit comparison between studies, particularly for immunity and risk factors for disease. Considerations for conducting future birth cohort studies on norovirus are discussed.

Norovirus is a common cause of acute gastroenteritis (AGE) among children in developing countries. Limited data on the prevalence and genetic variability of norovirus are available in Cameroon, where early childhood mortality due to AGE is common. We tested 902 fecal specimens from children younger than 5 years of age hospitalized with AGE between January 2010 and December 2013. Overall, 76 (8.4%) samples tested positive for norovirus, of which 83% (63/76) were among children < 12 months old. Most of the noroviruses detected were in children infected between July and December of each year. All norovirus-positive specimens were genotyped, with 80% (61/76) being GII.4 (three variants detected). Genotypes GI.2, GI.6, GII.1, GII.2, GII.3, GII.6, GII.16, GII.17, and GII.21 genotypes were also detected. Interestingly, GII.4 Sydney and GII.17 Kawasaki viruses were found as early as 2010, years before their emergence globally. This study suggests norovirus is a significant cause of moderate to severe gastroenteritis among young children in Cameroon. Results are important to highlight appropriate prevention and control strategies for reducing the burden of norovirus disease. This article is protected by copyright. All rights reserved.

Background: Noroviruses are the leading cause of acute gastroenteritis outbreaks worldwide. Clarifying the viral, host, and environmental factors (epidemiologic triad) associated with severe outcomes can help target public health interventions. Methods: Acute norovirus outbreaks reported to the National Outbreak Reporting System (NORS) in 2009-2016 were linked to laboratory-confirmed norovirus outbreaks reported to CaliciNet. Outbreaks were analyzed for differences in genotype (GII.4 vs non-GII.4), hospitalization, and mortality rates by timing, setting, transmission mode, demographics, clinical symptoms, and health outcomes. Results: A total of 3747 norovirus outbreaks were matched from NORS and CaliciNet. Multivariable models showed that GII.4 outbreaks (n = 2353) were associated with healthcare settings (odds ratio [OR], 3.94 [95% confidence interval {CI}, 2.99-5.23]), winter months (November-April; 1.55 [95% CI, 1.24-1.93]), and older age of cases (>/=50% aged >/=75 years; 1.37 [95% CI, 1.04-1.79]). Severe outcomes were more likely among GII.4 outbreaks (hospitalization rate ratio [RR], 1.54 [95% CI, 1.23-1.96]; mortality RR, 2.77 [95% CI, 1.04-5.78]). Outbreaks in healthcare settings were also associated with higher hospitalization (RR, 3.22 [95% CI, 2.34-4.44]) and mortality rates (RR, 5.65 [95% CI, 1.92-18.70]). Conclusions: Severe outcomes more frequently occurred in norovirus outbreaks caused by GII.4 and those in healthcare settings. These results should help guide preventive interventions for targeted populations, including vaccine development.

Noroviruses are the most frequent cause of epidemic acute gastroenteritis in the United States (US). Between September 2013 and August 2016, 2,715 genotyped norovirus outbreaks were submitted to CaliciNet. GII.4 Sydney viruses caused 58% of outbreaks during these years. A GII.4 Sydney variant with a novel GII.P16 polymerase emerged in November 2015, causing 60% of all GII.4 outbreaks in the 2015-2016 season. Multiple polymerase types were found associated with GII.2 (3), GII.3 (3), GII.4 Sydney (3), GII.13 (2) and GII.17 (2) genotypes, 4 of which included GII.P16 variants. GII.P16 polymerase sequences associated with GII.2 and GII.4 Sydney strains were nearly identical, suggesting common ancestry. Other common genotypes, each causing 5-17% of outbreaks in a season, included GI.3, GI.5, GII.2, GII.3, GII.6, GII.13 and GII.17 Kawasaki. Acquisition of alternative RNA polymerases by recombination is an important mechanism for norovirus evolution and a phenomenon that was shown to occur more frequently than previously recognized in the US. Continued molecular surveillance of norovirus strains, including typing of both polymerase and capsid genes, is important for monitoring emerging strains in our continued efforts to reduce the overall burden of norovirus disease.

BACKGROUND: Noroviruses are important enteric pathogens in humans and animals. Recently, we reported a novel canine norovirus (CaNoV) in dogs with diarrhea belonging to a new genogroup (GVI). No data are available on exposure of humans to this virus. METHODS: Sera from 373 small animal veterinarians and 120 age-matched population controls were tested for IgG antibodies to CaNoV by a recombinant virus like particle based enzyme-linked immunosorbent assay. RESULTS: Antibodies to CaNoV were found in 22.3% of the veterinarians and 5.8% of the control group (p < 0.001). Mean corrected OD450 values for CaNoV antibodies were significantly higher in small animal veterinarians compared to the control group. CONCLUSIONS: These findings suggest that CaNoV may infect humans and small animal veterinarians are at an increased risk for exposure to this virus. Additional studies are needed to assess if this virus is able to cause disease in humans.