In recent years, numerous viruses have been identified from ticks, and some have been linked to clinical cases of emerging tick-borne diseases. Chinese northeast frontier is tick infested. However, there is a notable lack of systematic monitoring efforts to assess the viral composition in the area, leaving the ecological landscape of viruses carried by ticks not clear enough. Between April and June 2017, 7101 ticks were collected to perform virus surveillance on the China–North Korea border, specifically in Tonghua, Baishan, and Yanbian. A total of 2127 Ixodes persulcatus were identified. Further investigation revealed the diversity of tick-borne viruses by transcriptome sequencing of Ixodes persulcatus. All ticks tested negative for tick-borne encephalitis virus. Transcriptome sequencing expanded 121 genomic sequence data of 12 different virus species from Ixodes persulcatus. Notably, a new segmented flavivirus, named Baishan Forest Tick Virus, were identified, closely related to Alongshan virus and Harz mountain virus. Therefore, this new virus may pose a potential threat to humans. Furthermore, the study revealed the existence of seven emerging tick-borne viruses dating back to 2017. These previously identified viruses included Mudanjiang phlebovirus, Onega tick phlebovirus, Sara tick phlebovirus, Yichun mivirus, and three unnamed viruses (one belonging to the Peribunyaviridae family and the other two belonging to the Phenuiviridae family). The existence of these emerging tick-borne viruses in tick samples collected in 2017 suggests that their history may extend further than previously recognized. This study provides invaluable insights into the virome of Ixodes persulcatus in the China–North Korea border region, enhancing our ongoing efforts to manage the risks associated with tick-borne viruses.

• Scientific question : The temporal dynamics in cytokine profiles throughout severe fever with thrombocytopenia syndrome (SFTS) progression, their association with clinical severity, and the modifying effects of demographic factors such as age and sex remain insufficiently delineated, necessitating comprehensive longitudinal analyses. • Evidence before this study: Previous studies highlighted cytokine storms in SFTS pathogenesis but were constrained by small samples and cross-sectional designs, lacking longitudinal, multi-center data on cytokine trajectories and their links to disease severity and patient demographics. • New findings: Our multi-center retrospective analysis (2010–2023) of 287 serum samples from high-incidence regions of China revealed that interleukin (IL)-6, interferon (IFN)-α, IL-8, and IFN-γ-induced protein 10 (IP-10) drove hyperinflammation during the acute phase, while IL-10 moderated immune activation and might promote viral persistence, with prolonged elevation of IL-8 and IP-10 in some patients suggesting heterogeneous recovery pathways. Severe cases exhibited significantly higher IL-10, IFN-γ, IL-6, IFN-α, tumor necrosis factor (TNF)-α, IL-8, and IP-10, highlighting their potential as severity biomarkers. At the same time, sex-based differences showed elevated IFN-γ and IL-8 levels in females, and older patients demonstrateed increased IL-10, IFN-γ, and IFN-α. The acute and recovery phases of SFTS demonstrated dynamic variations in immune regulation, and significant changes also occurred in the correlations between cytokines and antibodies. • Significance of the study: Our decade-long multicenter study provides a comprehensive understanding of the immunopathogenesis of SFTS by systematically delineating the temporal dynamics of cytokine profiles throughout the disease. This work establishes a theoretically robust foundation for further investigations into cytokine-targeted therapeutic strategies and the incorporation of predictive biomarkers into clinical practice, ultimately aiming to refine diagnostic methodologies and enhance clinical management.

What is already known about this topic? Severe fever with thrombocytopenia syndrome (SFTS) is a serious tick-borne disease in East Asia with high mortality, particularly affecting the elderly. Since its discovery in 2010, inconsistencies in small-scale studies and the lack of decade-long research on antibody levels in large population samples after natural infection, along with the absence of an effective vaccine, highlight the need for large-scale, long-term data in high-incidence regions of China. What is added by this report? This study of 1,410 serum samples from SFTS patients in high-incidence regions of China reveals that immunoglobulin M (IgM) levels peak at 8–14 days post-infection, declining to nearly undetectable levels by 180 days. Immunoglobulin G (IgG) and neutralizing antibodies (NAb) levels peak at 22–180 days, persisting up to 10 years. IgM levels correlate with viral load and various immune and coagulation parameters, with lower levels observed in fatal cases. During convalescence, elderly patients have lower IgG levels, whereas females exhibit higher IgG levels compared with males. What are the implications for public health practice? The study’s findings on long-term antibody dynamics in SFTS patients can significantly improve vaccine development, optimize therapy scheduling, inform public health policies, and enhance diagnostic tools, leading to better disease management and prevention in high-incidence areas.

In recent years, there have been significant advancements in the research of Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV). However, several limitations and challenges still exist. For instance, researchers face constraints regarding experimental conditions and the feasibility of sample acquisition for studying SFTSV. To enhance the quality and comprehensiveness of SFTSV research, we opted to employ PMA-induced THP-1 cells as a model for SFTSV infection. Multiple time points of SFTSV infection were designed to capture the dynamic nature of the virus–host interaction. Through a comprehensive analysis utilizing various bioinformatics approaches, including diverse clustering methods, MUfzz analysis, and LASSO/Cox machine learning, we performed dynamic analysis and identified key genes associated with SFTSV infection at the host cell transcriptomic level. Notably, successful clustering was achieved for samples infected at different time points, leading to the identification of two important genes, PHGDH and NLRP12. And these findings may provide valuable insights into the pathogenesis of SFTSV and contribute to our understanding of host–virus interactions.

What is already known about this topic? Mucosal IgA plays a crucial role in host immunity against respiratory viruses. Recent studies suggest that it has the potential to mitigate the transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant. However, a comprehensive population-based analysis examining mucosal IgA levels following the winter 2022 wave of the coronavirus disease 2019 (COVID-19) pandemic is yet to be conducted. What is added by this report? In our study involving 3,421 participants, we documented IgA responses subsequent to SARS-CoV-2 infection. A significant proportion of individuals sustained increased levels of IgA for over six months. These levels were also observed in individuals with prior infections who underwent asymptomatic reinfections, indicating an active production of IgA antibodies. Further, individuals with multiple vaccinations or severe symptoms tended to display elevated IgA levels after recovery. What are the implications for public health practice? IgA in the nasal mucosa is crucial for defense against SARS-CoV-2 infection. These insights can enhance our knowledge of immune responses following infection and have provided certain reference values for disease prevention and control strategies.

Severe Fever with thrombocytopenia syndrome (SFTS) is a highly fatal viral infectious disease that poses a significant threat to public health. Currently, the phase and pathogenesis of SFTS are not well understood, and there are no specific vaccines or effective treatment available. Therefore, it is crucial to identify biomarkers for diagnosing acute SFTS, which has a high mortality rate. In this study, we conducted differentially expressed genes (DEGs) analysis and WGCNA module analysis on the GSE144358 dataset, comparing the acute phase of SFTSV-infected patients with healthy individuals. Through the LASSO–Cox and random forest algorithms, a total of 2128 genes were analyzed, leading to the identification of four genes: ADIPOR1, CENPO, E2F2, and H2AC17. The GSEA analysis of these four genes demonstrated a significant correlation with immune cell function and cell cycle, aligning with the functional enrichment findings of DEGs. Furthermore, we also utilized CIBERSORT to analyze the immune cell infiltration and its correlation with characteristic genes. The results indicate that the combination of ADIPOR1, CENPO, E2F2, and H2AC17 genes has the potential as characteristic genes for diagnosing and studying the acute phase of SFTS virus (SFTSV) infection.