The recent discovery of the Yezo virus (YEZV) in Japan and China has raised particular concern due to its potential to cause human diseases ranging from mild febrile illnesses to severe neurological disorders. We report, for the first time, the detection of five YEZV isolates in I. persulcatus ticks from three regions of Russia. The analysis was performed using 5318 ticks of two Ixodes genus collected in 2024 from 23 regions of Russia. The minimum infection rate of YEZV in Russia among I. persulcatus ticks was 0.12% (95% CI: 0.05–0.28). The westernmost and northernmost YEZV detection points have been recorded. YEZV isolates circulating in Russia are genetically diverse. Protein domains of Russian YEZV isolates’ genomes were characterized using HMMER, AlphaFold 3, and InterProScan. The YEZV nucleoprotein (N) of Russian isolates has a racket-shaped structure with “head” and “stalk” domains similar to those of Orthonairovirus haemorrhagiae. The Lys261–Arg261 substitution in the YEZV N Chita 2024-1 isolate occurs in the α11 structure in the region of interaction with viral RNA. Our results show that the distribution area of YEZV is much wider than previously known, provide new data on complete YEZV genomes, extend our structural insight into YEZV N, and suggest a potential target for antiviral drug development to treat YEZV infection.

Though hundreds of thousands of papers are currently being published on HIV/AIDS, only tens of hundreds of them are devoted to the antibodies generated during the disease. Most of these papers discuss antibodies in HIV/AIDS as a diagnostic tool, and some articles describe neutralizing antibodies as a promising treatment. In this paper, we used affinity chromatography and ELISA to isolate natural IgG from the blood of 26 HIV-infected patients. IgG preparations were separated into the subfractions containing different types of light chains, and catalytic activities of subfractions were analyzed. Here, we show for the first time that the blood of HIV patients contains ~20% of bispecific κλ-IgG, presented with all IgG subclasses. Analysis of DNA-hydrolyzing and amylolytic activity show that most IgG preparations and subfractions are catalytically active. Our results expand the possible biological functions of natural IgG in HIV infection.

In 2025, high epizootic activity of highly pathogenic avian influenza virus (HPAIV) persisted globally, as evidenced by more than 7,000 outbreaks reported in poultry and wild birds across 75 countries, resulting in mortality or culling of birds exceeding 98 million specimens. The majority of outbreaks worldwide were associated with HPAIV A(H5N1) clade 2.3.4.4b, which has remained the predominant lineage in global circulation since 2021. In addition to the dominant A(H5N1) clade 2.3.4.4b subtype, circulation of other highly pathogenic subtypes was observed, including A(H5N5), A(H5N2), A(H5N8), and A(H5N9), as well as A(H7), indicating ongoing evolution of avian influenza viruses in natural and anthropogenic ecosystems. In the United States and several other countries, HPAIV A(H5N1) caused numerous infections in wild and domestic mammals as well as in humans. In 2025, the world’s first human case of A(H5N5) influenza was documented in the United States. A total of 74 zoonotic HPAIV human infections were reported globally in 2025, including 32 cases caused by A(H5) viruses of various clades (2.3.4.4b, 2.3.2.1e, 2.3.2.1a), reflecting a continuing increase in interspecies transmission that poses a potential public health threat. In the Russian Federation, high epizootic activity of HPAIV persisted throughout 2025, with outbreaks caused by A(H5N1) clade 2.3.4.4b viruses reported in both wild and domestic birds. Notably, in the Russian Far East, circulation of an A(H5N1) virus carrying mammalian-adaptive mutations associated with increased virulence in mammals was detected. Additionally, amino acid substitutions in antigenic sites were identified in several A(H5N1) isolates. Despite ongoing virus evolution, no substantial alterations in the antigenic properties of HPAIV A(H5N1) strains circulating in the Russian Federation have been observed to date.

Introduction: Seasonal influenza circulates in an epidemic pattern, with periodic shifts in the dominant subtype driven by antigenic drift and population immunity. Mutations in surface proteins – particularly within the hemagglutinin receptor-binding site (RBS) – enable the virus to evade host immune responses. Among these, the D222G/N substitution has been associated with increased virulence of A(H1N1)pdm09 viruses. Objective: Genetic characterization of viruses detected in influenza cases in the Russian Federation in the 2024–2025 epidemic season. Materials and methods: From September 10, 2024, to June 19, 2025, 1,931 specimens from patients with influenza, including 240 autopsy samples, were tested by RT-PCR. For 420 samples with sufficient genetic material, influenza virus genome sequences were obtained using NGS. Results: During the 2024–2025 flu season, A(H1N1)pdm09 viruses predominated in the Russian Federation. Influenza B/Victoria lineage viruses were less frequent while influenza A (H3N2) cases were sporadic. Most fatal cases occurred in individuals belonging to risk groups, with a notably low vaccination coverage among them. Among fatal A(H1N1)pdm09 cases, the HA-D222N mutation – a marker of enhanced virulence – was detected in the major viral variant in 19.0 % of sequenced samples. Additionally, D222G/N mutations were identified in minor variants in 10.1 % of fatal cases. Notably, the D222N mutation in the major variant was also found in one recovered A(H1N1)pdm09 case (0.5 %). Resistance markers to antiviral drugs – oseltamivir (1.9 %) and baloxavir marboxil (0.4 %) were detected in 6 of all sequenced A(H1N1)pdm09 viruses (2.3 %). Conclusion: The detection of HA-D222G/N mutations associated with increased virulence and fatality from A(H1N1)pdm09 viruses underscores the importance of vaccination as a key preventive measure, particularly for population groups at risk, and timely treatment for influenza.