Many high pathogenicity avian influenza (HPAI) cases in wild birds due to H5N1 HPAI virus (HPAIV) infection were reported in northern Japan in the winter of 2021–2022. To investigate the epidemiology of HPAIVs brought to Japan from surrounding areas, a genetic analysis of H5 HPAIVs isolated in northern Japan was performed, and the pathogenicity of the HPAIV in chickens was assessed by experimental infection. Based on the genetic analysis of the hemagglutinin gene, pathogenic viruses detected in northern Japan as well as one in Sakhalin, the eastern part of Russia, were classified into the same subgroup as viruses prevalent in Europe in the same season but distinct from those circulating in Asia in winter 2020–2021. High identities of all eight segment sequences of A/crow/Hokkaido/0103B065/2022 (H5N1) (Crow/Hok), the representative isolates in northern Japan in 2022, to European isolates in the same season could also certify the unlikeliness of causing gene reassortment between H5 HPAIVs and viruses locally circulating in Asia. According to intranasal challenge results in six-week-old chickens, 50% of the chicken-lethal dose of Crow/Hok was calculated as 10^4.5 times of the 50% egg-infectious dose. These results demonstrated that the currently prevalent H5 HPAIVs could spread widely from certain origins throughout the Eurasian continent, including Europe and the Far East, and implied a possibility that contagious viruses are gathered in lakes in the northern territory via bird migration. Active monitoring of wild birds at the global level is essential to estimate the geographical source and spread dynamics of HPAIVs.

In the fall of 2022, high pathogenicity avian influenza viruses (HPAIVs) were detected from raptors and geese in Japan, a month earlier than in past years, indicating a shift in detection patterns. In this study, we conducted a phylogenetic analysis on H5N1 HPAIVs detected from six wild birds during the 2022/2023 season to determine their genetic origins. Our findings revealed that these HPAIVs belong to the G2 group within clade 2.3.4.4b, with all isolates classified into three subgroups: G2b, G2d, and G2c. The genetic background of the G2b virus (a peregrine falcon-derived strain) and G2d viruses (two raptors and two geese-derived strains) were the same as those detected in Japan in the 2021/2022 season. Since no HPAI cases were reported in Japan during the summer of 2022, it is probable that migratory birds reintroduced the G2b and G2d viruses. Conversely, the G2c virus (a raptor-derived strain) was first recognized in Japan in the fall of 2022. This strain might share a common ancestor with HPAIVs from Asia and West Siberia observed in the 2021/2022 season. The early migration of waterfowl to Japan in the fall of 2022 could have facilitated the early invasion of HPAIVs.

We developed a method to determine the sequences of hemagglutinin (HA) and neuraminidase (NA) from RNA extracted directly from wild bird fecal samples, using Nanopore Flongle. We determined the nucleotide sequences and subtypes of HA and NA in 16 and 15 samples respectively, using Flongle. The results of HA and NA subtyping determined by the conventional method were consistent with their subtypes determined by our method, thereby the applicability of this method in the identification of HA and NA subtypes. In addition, the homology between the HA fragments in this and the Sanger methods ranged from 98.5 % to 100 %. Compared with conventional PCR with the Sanger method, this method can easily determine HA and NA subtypes and sequences directly from the fecal samples. It is easier to implement and has lower running costs (USD100$) than other NGS-based methods, making it a useful tool for avian influenza surveillance in wild birds.

Genetic and antigenic analyses were performed on highly pathogenic avian influenza viruses (HPAIVs) isolated in Hokkaido, northern Japan, during the winter of 2024–2025. Ninety-eight HPAIVs were isolated from feces of waterfowl, tracheal swabs from dead wild birds, or lung homogenates from dead chickens. Phylogenetic analysis of the hemagglutinin (HA) gene from 47 representative isolates revealed that all sequences belonged to the G2d subgroup of clade 2.3.4.4b H5HA, which has been the dominant lineage in Hokkaido since the winter of 2021–2022. These isolates were further divided into three major groups within the subgroup. The HPAIVs isolated in the Republic of Korea, China, and North America were genetically closely related to the Hokkaido isolates, whereas no HPAIVs genetically related to European strains or those detected in North American cattle were identified. Furthermore, HPAIVs isolated from seabirds were genetically closely related to those found in dead marine mammals along the eastern coast of Hokkaido in the spring of 2025. No apparent antigenic differences were observed between the HPAIVs isolated in this study and those from previous seasons. These findings highlight the wide distribution of HPAIVs in Hokkaido, particularly from Asian and North American lineages, and underscore the importance of continuous surveillance.

The Indian rhinoceros (Rhinoceros unicornis) is a large herbivore found in northern India and southern Nepal. It is a critically endangered species, with an estimated population of approximately 3,600 in the wild. Genetic factors, such as the loss of genetic diversity and the accumulation of deleterious variations, are critical risk factors for the extinction of endangered species, such as the Indian rhinoceros. To support the conservation efforts of the Indian rhinoceros, we assembled its draft genome. The new genomic data will enable the study of functional genes associated with the ecological and physiological characteristics of Indian rhinoceros and help us establish more effective conservation measures. The muscles of an Indian rhinoceros that died from prostration at a zoo were collected, and the samples were stored at the National Institute for Environmental Studies (Tsukuba, Japan). Sequence data were obtained using an Illumina NovaSeq 6000 platform for short reads and an Oxford Nanopore Technologies PromethION for long reads. We generated approximately 235.2 Gbp of data. From these sequences, we assembled a 2,375,051,758 bp genome consisting of 7,615 contigs. The genome data are available from the National Center Biotechnology Information BioProject database under accession number BOSQ00000000.