Impact of the COVID-19 pandemic on norovirus circulation in Germany

A broadly protective human antibody for GI genogroup noroviruses

Noroviruses infect millions each year, and while effective countermeasures are eagerly sought, none have been reported for the GI genogroup, first described more than 50 years ago. Here, to provide insight into GI norovirus neutralization, we isolated a broad GI antibody, 16E10, from a human blood donor and showed it neutralizes noroviruses in human enteroid cultures and abrogates or reduces infection in rhesus macaques. The cryogenic electron microscopy reconstruction of 16E10 with a norovirus protruding-domain dimer at 2.56-Å resolution reveals an exceptionally large binding surface, overlapping an antibody supersite, distal from host receptor-binding or cofactor-binding sites. Cryogenic electron microscopy reconstructions with virus-like particles (VLPs) showed that 16E10 disrupts protruding domains on the VLP surface and disassembles VLPs, altering viral organization required for avidity. While its epitope was generally conserved, 16E10 recognized multiple sequence-divergent residues, binding to which was enabled by corresponding cavities in the 16E10-norovirus interface. Broad recognition of noroviruses can thus incorporate sequence-divergent residues, through a cavity-based mechanism of diversity tolerance.

Eight Years of Norovirus Surveillance in Urban Wastewater: Insights from Next-Generation

Human noroviruses (HNoVs) are a leading cause of acute gastroenteritis worldwide, with significant public health implications. In this study, wastewater-based epidemiology (WBE) was used to monitor the circulation and genetic diversity of HNoVs in Rome over an eight-year period (2017-2024). A total of 337 wastewater samples were analyzed using RT-nested PCR and next-generation sequencing (NGS) to identify genogroups GI and GII and their respective genotypes. The results showed that GII had higher detection rates (66.5%) compared to GI (50.7%), with significant variation between years. Detection rates peaked in 2019 before declining sharply in 2020, coinciding with the COVID-19 pandemic and rebounding after the pandemic in 2023. A total of 24 genotypes were identified (8 GI and 17 GII), including persistent variants GII.2, GII.3 and GII.4 and emerging genotypes such as GII.8, GII.10 and GII.14. Only two GII.4 variants, Sydney_2016 and Sydney_2012, were detected in the study. These results demonstrate the utility of WBE in tracking HNoVs circulation, identifying genotype diversity and capturing shifts in transmission dynamics. WBE provides a cost-effective and comprehensive tool for public health surveillance, particularly in regions with limited clinical surveillance. Sustained investment in WBE is crucial for advancing our understanding of HNoVs epidemiology and its long-term trends.

Children hospitalised with gastroenteritis before and during the COVID-19 pandemic

AIMS

The COVID-19 pandemic altered the pattern of many paediatric infections. We aimed to assess the incidence and characteristics of children hospitalised with gastroenteritis during the early and the late pandemic, relative to previous years.

METHODS

In a retrospective study, we collected data from patient files of children aged 1 month to 5 years, admitted with gastroenteritis to a paediatric department in Denmark during January-June, of 2017 to 2021, comparing incidence rates and clinical features in the early pandemic (March to June 2020), and late pandemic period (January to June 2021), to similar pre-pandemic months.

RESULTS

In the early pandemic, admission rates per 1000 children/month declined to 0.5 (95% CI: 0.3-0.6) from pre-pandemic rates of 1.6 (95% CI: 1.4-1.7) (p < 0.0001) and increased in the late pandemic to 2.2 (95% CI: 1.9-2.6) (p = 0.006). Children admitted in the late pandemic period were older than those admitted previously.

CONCLUSION

A resurgence of gastroenteritis in children occurred in the spring of 2021, with higher hospital admission rates of children, who were older, but not more severely ill than previously.

Pathogen dynamics and discovery of novel viruses and enzymes by deep nucleic acid sequencing of wastewater

Wastewater contains an extensive reservoir of genetic information, yet largely unexplored. Here, we analyzed by high-throughput sequencing total nucleic acids extracted from wastewater samples collected during a 17 month-period in Berlin, Germany. By integrating global wastewater datasets and applying a novel computational approach to accurately identify viral strains within sewage RNA-sequencing data, we demonstrated the emergence and global dissemination of a specific astrovirus strain. Astrovirus abundance and sequence variation mirrored temporal and spatial patterns of infection, potentially serving as footprints of specific timeframes and geographical locations. Additionally, we revealed more than 100,000 sequence contigs likely originating from novel viral species, exhibiting distinct profiles in total RNA and DNA datasets and including undescribed bunyaviruses and parvoviruses. Finally, we identified thousands of new CRISPR-associated protein sequences, including Transposase B (TnpB), a class of compact, RNA-guided DNA editing enzymes. Collectively, our findings underscore the potential of high-throughput sequencing of total nucleic acids derived from wastewater for a broad range of applications.

Identifying SNP threshold from P2 sequences for investigating norovirus transmission

Noroviruses are a group of non-enveloped single-stranded positive-sense RNA virus belonging to Caliciviridae family. They can be transmitted by the fecal-oral route from contaminated food and water and cause mainly acute gastroenteritis. Outbreaks of norovirus infections could be difficult to detect and investigate. In this study, we developed a simple threshold detection approach based on variations of the P2 domain of the capsid protein. We obtained sequences from the norovirus hypervariable P2 region using Sanger sequencing, including 582 pairs of epidemiologically-related strains from 35 norovirus outbreaks and 6402 pairs of epidemiologically-unrelated strains during the four epidemic seasons. Genetic distances were calculated and a threshold was performed by adopting ROC (Receiver Operating Characteristic) curve which identified transmission clusters in all tested outbreaks with 80 % sensitivity. In average, nucleotide diversity between outbreaks was 67.5 times greater than the diversity within outbreaks. Simple and accurate thresholds for detecting norovirus transmissions of three genotypes obtained here streamlines molecular investigation of norovirus outbreaks, thus enabling rapid and efficient responses for the control of norovirus.

Epidemiological Features of Human Norovirus Genotypes before and after COVID-19 Countermeasures in Osaka, Japan

We investigated the molecular epidemiology of human norovirus (HuNoV) in all age groups using samples from April 2019 to March 2023, before and after the COVID-19 countermeasures were implemented. GII.2[P16] and GII.4[P31], the prevalent strains in Japan before COVID-19 countermeasures, remained prevalent during the COVID-19 pandemic, except from April to November 2020; in 2021, the prevalence of GII.2[P16] increased among children. Furthermore, there was an increase in the prevalence of GII.4[P16] after December 2022. Phylogenetic analysis of GII.P31 RdRp showed that some strains detected in 2022 belonged to a different cluster of other strains obtained during the present study period, suggesting that HuNoV strains will evolve differently even if they have the same type of RdRp. An analysis of the amino acid sequence of VP1 showed that some antigenic sites of GII.4[P16] were different from those of GII.4[P31]. The present study showed high infectivity of HuNoV despite the COVID-19 countermeasures and revealed changes in the prevalent genotypes and mutations of each genotype. In the future, we will investigate whether GII.4[P16] becomes more prevalent, providing new insights by comparing the new data with those analyzed in the present study.