First report of norovirus sequences isolated from raccoon dogs in mainland China

Emerging zooanthroponotic risks: Detection of the human norovirus GII.4 Sydney[P31] strain in a domestic dog in Brazil

Recent increases in zoonotic diseases underscore the integration of companion animals into urban environments, posing complex transmission risks and highlighting the necessity of One Health approaches. Respiratory and enteric viruses have been consistently linked to interspecies transmission between humans and animals. This study aimed to assess the circulation of human noroviruses (NoV), human adenoviruses (HAdV), enteroviruses (EV), parechoviruses (PeV-A), human bocaviruses (HBoV), hepatitis A (HAV) and E viruses (HEV), Influenza A and B viruses (Flu A/B), respiratory syncytial virus (RSV), and SARS-CoV-2 in domestic dogs and cats in Brazil to understand potential zooanthroponosis risks. Between 2012 and 2021, 600 fecal samples from dogs and cats (516 and 84, respectively) were collected at small animal clinics in São Paulo state, Brazil. The specimens underwent in-house qPCR screening for HBoV and HAdV, while EV, PeV-A, NoV, and HEV were tested using in-house RT-qPCR. SARS-CoV-2, Flu A/B, and RSV were investigated with a commercial RT-qPCR kit assay. HAV detection utilized conventional nested (RT)-PCR. Positive samples were sequenced for molecular characterization and phylogenetic analysis. NoV was detected in 0.2 % (1/600) of the animals, while all other investigated viruses tested negative. The NoV-positive sample, collected in 2012 from a pet dog, was identified as genotype GII.4_Sydney[P31]. The Dog/BRA/2012/GII.4_Sydney[P31]/IAL-M21 strain exhibited a close genetic relationship to Brazilian human and environmental NoV GII.4_Sydney[P31] strains, with 98.1-99.2 % nucleotide similarity in ORF1 and 99.2-99.6 % in ORF2 sequences, suggesting interspecies transmission. Pet dogs are frequently exposed to human fecal-borne viruses, highlighting the potential for zooanthroponotic transmission due to their close interaction with humans in shared environments. There is an urgent need to enhance surveillance studies in companion animals to better understand the implications of detecting human NoV strains in pets, as NoV could potentially act as a reverse zoonotic disease in households, animal hospitals, or shelters worldwide.

Recent insights into reverse genetics of norovirus

Norovirus is the leading cause of viral gastroenteritis globally, and poses substantial threats to public health. Despite substantial progress made in preventing norovirus diseases, the lack of a robust virus culture system has hampered biological research and effective strategies to combat this pathogen. Reverse genetic system is the technique to generate infectious viruses from cloned genetic constructs, which is a powerful tool for the investigation of viral pathogenesis and for the development of novel drugs and vaccines. The strategies of reverse genetics include bacterial artificial chromosomes, vaccinia virus vectors, and entirely plasmid-based systems. Since each strategy has its pros and cons, choosing appropriate approaches will greatly improve the efficiency of virus rescue. Reverse genetic systems that have been employed for norovirus greatly extend its life cycle and facilitate the development of medical countermeasures. In this review, we summarize the current knowledge on the structure, transmission, genetic evolution and clinical manifestations of norovirus, and describe recent advances in the studies of norovirus reverse genetics as well as its future prospects for therapeutics and vaccine development.

Investigation of genotype diversity of 7,804 norovirus sequences in humans and animals of China

Norovirus is a prominent enteric virus responsible for severe acute gastroenteritis disease burden worldwide. In our current study, we analyzed 7,804 norovirus sequences of human and animals in China which were detected from 1980 to 2020 from GenBank. The GenBank database was searched up to May 2021 with the following search terms: "norovirus" or "norwalk virus" and "China." The 7,804 norovirus sequences were collected and evaluated by phylogenetic analysis using MEGA X software package. The online typing tool (https://www.rivm.nl/mpf/typingtool/norovirus/) was used to confirm the genotypes. There were 36 norovirus genotypes prevailing in China. GII.4 was the most prevalent genotype, and GII.2, GII.3 and GII.17 also emerged during different time periods. Most sequences were detected in East China (41.72%, 3,256/7,804), but different norovirus genotypes were distributed widely across the country. A variety of norovirus genotypes, including GI, GII, GIII, GIV, GV, GVI, GVII and GX, were reported in different animals. Furthermore, a GI.3 sequence detected from animal had high identity with norovirus detected in human from the same region, indicating the potential norovirus zoonotic transmission in China. In conclusion, these results indicated that norovirus sequences with considerable genetic diversity distributed widely in China, with potential reverse zoonotic transmission from human to animals.