Mosquito viruses cause unpredictable outbreaks of disease. Recently, several unassigned viruses isolated from mosquitoes, including the Omono River virus (OmRV), were identified as totivirus-like viruses, with features similar to those of the Totiviridae family. Most reported members of this family infect fungi or protozoans and lack an extracellular life cycle stage. Here, we identified a new strain of OmRV and determined high-resolution structures for this virus using single-particle cryo-electron microscopy. The structures feature an unexpected protrusion at the five-fold vertex of the capsid. Disassociation of the protrusion could result in several conformational changes in the major capsid. All these structures, together with some biological results, suggest the protrusions’ associations with the extracellular transmission of OmRV. Mosquito is a reservoir of viruses, with a large amount of them perform significant research value. Omono River virus (OmRV) has been isolated from Culex mosquito and is closely related to the family Totiviridae. However, current researches have reported the extracellular transmission ability of OmRV, which is lacked in most members of Totiviridae. In the current study, we isolated a new strain, OmRV-LZ, and obtained its high-resolution cryo-electron microscopy (cryo-EM) structure. Unexpectedly, a protrusion structure has been found located at the five-fold vertex, which is unrecognized in the previous studies. Structural and molecular biological experiments were applied to try to investigate its functions. The results may be helpful to understand the extracellular transmission ability of OmRV-LZ and similar double-stranded RNA (dsRNA) viruses.

Background: After the adjustment of COVID-19 epidemic policy, mainland China experienced two consecutive waves of Omicron variants within a seven-month period. In Guangzhou city, as one of the most populous regions, the viral infection characteristics, molecular epidemiology, and the dynamic of population immunity are still elusive. Methods: We launched a prospective cohort study in the Guangdong Provincial CDC from December 2022 to July 2023. Fifty participants who received the same vaccination regimen and had no previous infection were recruited. Results: 90% of individuals were infected with Omicron BA.5* variants within three weeks in the first wave. Thirteen cases (28.26%) experienced infection with XBB.1* variants, occurring from 14 weeks to 21 weeks after the first wave. BA.5* infections exhibited higher viral loads in nasopharyngeal sites compared to oropharyngeal sites. Compared to BA.5* infections, the XBB.1* infections had significantly milder clinical symptoms, lower viral loads, and shorter durations of virus positivity. The infection with the BA.5* variant elicited varying levels of neutralizing antibodies against XBB.1* among different individuals, even with similar levels of BA.5* antibodies. The level of neutralizing antibodies specific to XBB.1* determined the risk of reinfection. Conclusions: The rapid large-scale infections of the Omicron variants have quickly established herd immunity among the population in mainland China. In the future of the COVID-19 epidemic, a lower infection rate but a longer duration can be expected. Given the large population size and ongoing diversified herd immunity, it remains crucial to closely monitor the molecular epidemiology of SARS-CoV-2 for the emergence of new variants of concern in this region. Additionally, the timely evaluation of the immune status across different age groups is essential for informing future vaccination strategies and intervention policies.

Salmonella enterica is a leading foodborne pathogen worldwide, posing significant public health concerns. However, its prevalence in mountainous regions in China remains unclear. This study analyzed 384 Salmonella strains isolated from 2,540 samples collected between 2017 and 2024 from humans, food, and environmental sources in tropical mountainous areas of China. Whole-genome sequencing and antimicrobial-susceptibility testing were performed to investigate genomic characteristics and antimicrobial resistance profiles. The results showed that S . I 1,4 [5],12:i:- (ST34, 43.5%) was the predominant serovar among diarrheal patients, while S . Enteritidis (ST11, 40%) was the primary causative serovar associated with systemic infections characterized by bacteremia. In food and environmental samples, S . Typhimurium (ST19, 39.1%) and S . Enteritidis (ST11, 35.1%) were most frequently isolated, respectively. Antimicrobial susceptibility testing revealed high resistance rates to ampicillin (63.8%), tetracycline (62.7%), ciprofloxacin (17.7%), cefotaxime (16.4%), and ceftazidime (15.6%), with 115 isolates (29.9%) identified as multidrug-resistant. Notably, six isolates were tigecycline-resistant, including two harboring tet(X4 ) genes on an IncFIA(HI1)-IncHI1A- IncHI1B(R27) hybrid plasmid. The distribution of virulence genes varied across strains from different sources and serovars. Genes encoding carbonic anhydrase ( mig-5 ), plasmid-encoded fimbriae ( pefA , pefB , pefC , and pefD ), and type III secretion system effectors ( spvB , spvC , and spvD ) were significantly more prevalent in strains from patients with systemic infection than in those from diarrhea cases. The cdtB gene encoding typhoid toxin was identified in 19 non-typhoidal strains. This study presents the first comprehensive report on the prevalence and genetic dynamics of S. enterica in tropical mountainous regions of southern China, offering insights into novel interventions. IMPORTANCE: Salmonella is a serious zoonotic foodborne pathogen and the third leading cause of death from human diarrheal diseases worldwide. In this study, we report, for the first time, a systematic surveillance of Salmonella prevalence among clinical patients, food, and environmental sources in the tropical mountainous regions of southern China from 2017 to 2024. Our findings illuminate the prevalence and genetic dynamics of S. enterica across diverse sources, as well as differences between patients with diarrheal disease and those with systemic infections characterized by bacteremia. Moreover, we observed high resistance to clinically important treatment drugs, including fluoroquinolones and third-generation cephalosporins, in these regions. These results provide critical evidence to inform more effective surveillance, treatment, and control strategies in tropical settings and underscore the need for continuous, real-time monitoring of pathogen dynamics.

Chikungunya virus (CHIKV) poses an increasing global public health threat, as evidenced by the significant 2025 Foshan outbreak in China. Rapid, whole-genome sequencing (WGS) is critical for outbreak response but is challenged by primer mismatches across diverse lineages and a lack of direct sequencing platform comparisons. To address this, we developed a novel lineage-inclusive primer set and performed parallel WGS on 24 clinical samples from the outbreak using both Illumina (NGS) and Oxford Nanopore Technologies (TGS) platforms. Our lineage-inclusive primer set successfully amplified full-length CHIKV genomes across all samples. Comparisons revealed that Illumina NGS provided higher raw read accuracy, while Nanopore TGS achieved more complete coverage of terminal UTRs with a faster turnaround time. Crucially, after polishing, variant calls between the two platforms were 100% concordant. Phylogenetic analysis was consistent with a single introduction event, with all outbreak isolates forming a monophyletic clade within the ECSA lineage most closely related to contemporaneous strains from Réunion Island. This study validates a lineage-inclusive amplicon-based sequencing strategy and demonstrates that NGS and TGS offer complementary advantages. When integrated, they provide a robust framework for real-time genomic surveillance, enhancing preparedness and guiding public health interventions against CHIKV.

Titanium dioxide nanoparticles (nTiO₂) possess unique physicochemical properties, such as large specific surface area, enabling heavy metals adsorption like Cadmium (Cd), yet the combined risks to the ecosystem and human remain unclear. This 90-day study explored the combined effects of nTiO₂ (at a population-relevant dose of 100 mg/kg body weight administered via gavage) and cadmium chloride (CdCl₂) (50 mg Cd/L by drinking water) on kidney and gut microbiota of rats. Co-exposure of nTiO₂ and Cd significantly reduced the nephrotoxicity induced by Cd, with lower levels of urine biochemical indicators and Cd content, milder histopathological changes and ultrastructural damage. A two-way ANOVA analysis suggested antagonism between nTiO₂ and Cd on urinary creatinine (CRE) and Urea. Coincidentally, gut microbiota remained unaffected by nTiO₂ but was disrupted by Cd. Co-exposure also partially alleviated the adverse changes, restoring the decreased Beta-diversity and the relative abundance of bacteria to control levels. Furthermore, co-exposure resulted in a 19.2 % decline in the blood Cd concentration and an 8.6 % reduction in kidney, while the Cd content of 24 h feces was 3.6 % higher. These findings suggested antagonistic effects of nTiO₂ against Cd-induced nephrotoxicity and intestinal flora disorder in rats. The effects might be attributed to the adsorption of nTiO₂ on Cd, which resulted in the reduced Cd intake and distribution, coupled with increased excretion, thereby decreasing the Cd bioavailability. This study provides new evidence for understanding the impacts of nTiO₂ and Cd on mammals and will contribute to the further risk assessments of co-exposure to human health and environment safety.