Objective:This study analyzed the epidemiological characteristics of the clustered cases of severe fever with thrombocytopenia syndrome (SFTS) in Jiangsu province, so as to provide a scientific basis for prevention and control efforts.Methods:In this study we searched for cases related to clustered outbreaks and conducted epidemiological investigations of the cases, their co-exposed individuals, and close contacts. The basic information of the cases and their disease progression were collected and documented. The source of infection and transmission routes were analyzed. Fisher’s exact probability test and independent samples t-test were used to compare the differences between index and secondary cases. Results:From 2018 and 2024, a total of nine cluster outbreaks were reported in Jiangsu province, involving 32 cases of SFTS with 12 fatalities. Seven clustered outbreaks occurred in rural communities, while two occurred in medical institutions. The primary cause of these outbreaks was direct contact with confirmed cases.Conclusions:In recent years, Jiangsu province has experienced multiple clustered outbreaks of SFTS. Targeted health education should be implemented in high-risk areas to increase awareness of personal protective measures. Medical institutions should standardize the management of confirmed cases, educate patients′ families about prevention and control measures, and strengthen training for healthcare workers to ensure effective infection control within hospitals.

Objective:To investigate the G/P genotypes of group A rotavirus（RVA）in the 2023 sentinel surveillance in Jiangsu Province，and to conduct a molecular characterization analysis of the whole-genome sequences of four G9P［4］genotype RVA strains identified during surveillance.Methods:A total of 212 RVA-positive specimens collected from the surveillance system in 2023 were subjected to G/P genotyping using multiplex nested RT-PCR. Whole-genome sequencing was performed on six G9P［4］strains. The resulting complete genome sequences were preliminarily genotyped using BLAST，followed by comprehensive molecular characterization analyses utilizing BioEdit 7.0.5，MAFFT，MEGA 7.0，and iTOL software.Results:The overall RVA positivity rate was 6.22%. The predominant G/P combination in both outpatient and inpatient settings was G8P［8］. Among the six G9P［4］strains，four were successfully sequenced. All four exhibited the genotype constellation G9-P［4］-I2-R2-C2-M2-A2-N1-T2-E2-H2. While the NSP2 gene belonged to the N1 genotype，all other genes corresponded to the DS-1-like genogroup. Phylogenetically，the four Jiangsu G9P［4］strains clustered within Lineage V of the VP7 gene and formed a distinct minor subclade within the N1 branch of the NSP2 gene. Unique amino acid substitutions were identified at multiple VP7 neutralization antigenic epitope sites when compared to vaccine strains.Conclusions:The predominant circulating RVA strain in Jiangsu province during 2023 was G8P［8］. Concurrently，the relatively uncommon G9P［4］-N1 strain was detected. This strain exhibited significant amino acid differences at key epitopes compared to vaccine strains. Enhancing the proportion of whole-genome sequencing in RVA surveillance is warranted to obtain more detailed genetic information，thereby providing crucial data to support future vaccine development and optimization strategies.

Objective:To investigate the G/P genotypes of group A rotavirus（RVA）in the 2023 sentinel surveillance in Jiangsu Province，and to conduct a molecular characterization analysis of the whole-genome sequences of four G9P［4］genotype RVA strains identified during surveillance.Methods:A total of 212 RVA-positive specimens collected from the surveillance system in 2023 were subjected to G/P genotyping using multiplex nested RT-PCR. Whole-genome sequencing was performed on six G9P［4］strains. The resulting complete genome sequences were preliminarily genotyped using BLAST，followed by comprehensive molecular characterization analyses utilizing BioEdit 7.0.5，MAFFT，MEGA 7.0，and iTOL software.Results:The overall RVA positivity rate was 6.22%. The predominant G/P combination in both outpatient and inpatient settings was G8P［8］. Among the six G9P［4］strains，four were successfully sequenced. All four exhibited the genotype constellation G9-P［4］-I2-R2-C2-M2-A2-N1-T2-E2-H2. While the NSP2 gene belonged to the N1 genotype，all other genes corresponded to the DS-1-like genogroup. Phylogenetically，the four Jiangsu G9P［4］strains clustered within Lineage V of the VP7 gene and formed a distinct minor subclade within the N1 branch of the NSP2 gene. Unique amino acid substitutions were identified at multiple VP7 neutralization antigenic epitope sites when compared to vaccine strains.Conclusions:The predominant circulating RVA strain in Jiangsu province during 2023 was G8P［8］. Concurrently，the relatively uncommon G9P［4］-N1 strain was detected. This strain exhibited significant amino acid differences at key epitopes compared to vaccine strains. Enhancing the proportion of whole-genome sequencing in RVA surveillance is warranted to obtain more detailed genetic information，thereby providing crucial data to support future vaccine development and optimization strategies.

Objective:This study analyzed the epidemiological characteristics of the clustered cases of severe fever with thrombocytopenia syndrome (SFTS) in Jiangsu province, so as to provide a scientific basis for prevention and control efforts.Methods:In this study we searched for cases related to clustered outbreaks and conducted epidemiological investigations of the cases, their co-exposed individuals, and close contacts. The basic information of the cases and their disease progression were collected and documented. The source of infection and transmission routes were analyzed. Fisher’s exact probability test and independent samples t-test were used to compare the differences between index and secondary cases. Results:From 2018 and 2024, a total of nine cluster outbreaks were reported in Jiangsu province, involving 32 cases of SFTS with 12 fatalities. Seven clustered outbreaks occurred in rural communities, while two occurred in medical institutions. The primary cause of these outbreaks was direct contact with confirmed cases.Conclusions:In recent years, Jiangsu province has experienced multiple clustered outbreaks of SFTS. Targeted health education should be implemented in high-risk areas to increase awareness of personal protective measures. Medical institutions should standardize the management of confirmed cases, educate patients′ families about prevention and control measures, and strengthen training for healthcare workers to ensure effective infection control within hospitals.

Objective:To develop an integrated point-of-care testing (POCT) reagent for genotying respiratory syncytial virus (RSV) and evaluate its performance.Methods:Specific primers and probes were designed based on the conserved sequences of the genomes of RSV A and B as well as ON1 and BA9 genotypes. The PCR reaction system and conditions were optimized. The vitrification technology of reagents and multiplex detection platform were integrated to develop the RSV genotyping POCT reagent. The sensitivity, specificity, reproducibility, and clinical performance of the product were then evaluated.Results:The sensitivity of the developed integrated RSV genotyping POCT reagent reached 500 copies/ml. It exhibited good specificity with no cross-reaction with clinically similar pathogens. The coefficient of variation of Ct values for both inter-batch and intra-batch reproducibility was less than 5%, indicating good reproducibility. In testing 53 clinical samples, the detection results showed high consistency and concordance with the reference reagent, with a positive concordance rate of up to 98.11%.Conclusions:The developed integrated RSV genotyping POCT reagent incorporates nucleic acid extraction, purification, and detection into a single process, achieving a "sample in, result out" workflow. It is simple to operate and provides accurate, reliable, and stable detection results. This product can be used for the genotyping of RSV A and B in POCT, offering support for the prevention, control, and diagnosis of RSV.

Objective:To study the distribution of species type, biotype and genotype of human Brucella isolated and identified in Nanjing. Methods:A total of 89 strains of human Brucella were collected from microbiology laboratories of three sentinel hospitals in Nanjing from 2017 to 2022. The species type was identified using biological methods and Brucella nucleic acid detection (BCSP31-PCR and AMOS-PCR). Further biotyping of Brucella melitensis isolates was conducted by serological results of A and M factors. Meanwhile, genotype analysis was performed using multiple-locus variable number tandem repeat analysis (MLVA), multilocus sequence typing (MLST) and single nucleotide polymorphism (SNP). Results:From 2017 to 2022, 89 strains of Brucella isolated and identified in Nanjing were all Brucella melitensis. Among them, Brucella melitensis biotype 3 accounted for 82.02% (73/89), and biotype 1 accounted for 17.98% (16/89). MLVA typing showed that 89 strains of Brucella melitensis belong to the "Eastern Mediterranean" cluster and could be divided into 50 MLVA genotypes; among which panel 1 had 3 genotypes, namely Type 42 (84.27%, 75/89), Type 63 (8.99%, 8/89) and Type 43 (6.74%, 6/89). The results of MLST-9 and MLST-21 were both ST8, and the core genome multilocus sequence typing (cgMLST) classified 89 strains into 11 genotypes. SNP analysis revealed a total of 4 013 SNP loci, with SNPs ranging from 0 to 409 across different strains, involving 59 SNP genotypes. Conclusions:The human Brucella strains isolated and identified in Nanjing are all Brucella melitensis, mainly biotype 3. The MLVA cluster is the "Eastern Mediterranean" cluster. The traditional MLST-9 and MLST-21 typing results are all ST8 type, while cgMLST divides all the strains into 11 genotypes with higher resolution.

Objective:To explore the application of COVID-19-specific IgG antibody in identifying epidemic Omicron BA.5 strain infection.Method:Omicron BF.7/BA.5 naturally infected population, healthy population vaccinated with the COVID-19 vaccine, and Omicron BF.7/BA.5 breakthrough cases were enrolled into this study. The serum WT-S-IgG and BA.5-S-IgG were detected by indirect ELISA, and the serum-specific IgG antibody levels of different populations were compared. The application value of the two antibody titers and the ratio of the two antibodies in identifying Omicron BA.5 epidemic strain infection were explored by the ROC curve, aiming to provide technical support for pathogen diagnosis.Results:The antibody titers of WT-S-IgG and BA.5-S-IgG in the breakthrough cases were higher than those in the naturally infected population and the healthy population ( P<0.05). The area under the curve (AUC) of WT-S-IgG and BA.5-S-IgG in identifying epidemic Omicron BA.5 strain infection was 0.947 and 0.961, respectively. The AUC of BA.5-S-IgG and WT-S-IgG antibody titer ratio was 0.873. When the antibody titer ratio was 0.855, the sensitivity and specificity were 80.00% and 90.00%, respectively. According to the interval since the last infection, the AUC of the ratio of BA.5-S-IgG to WT-S-IgG antibody titer to identify the infection of epidemic strains less than 30 days and more than 30 days was 0.887 and 0.863, respectively, and the sensitivity and specificity were both above 80%. Conclusion:Both BA.5-S-IgG and WT-S-IgG, as well as the combination of these two antibodies, are of high value in the identification of epidemic strains.

Objective:To retrospectively analyze the molecular epidemiological features and genetic recombination of coxsackievirus A4 (CVA4) strains isolated in Jiangsu from 2015 to 2022.Methods:Throat or anal swab samples were collected from patients with herpangina or hand, foot and mouth disease (HFMD). Real-time PCR was used to detect CVA4. A comprehensive and systematic phylogenetic analysis was conducted based on 72 whole genomes and 99 VP1 sequences of CVA4 strains. Several bioinformatics software including DNAStar, MEGA7.0 and Similarity plots3.5.1 was used for analysis of homology, genetic recombination and amino acid variation sites.Results:Four genotypes (A, B, C and D) and five sub-genotypes (C1-C5) of CVA4 were identified based on the VP1 nucleotide sequences. C2 was the predominant sub-genotype causing HFMD. The Jiangsu strains showed high homology with the CVA4 prototype in the P1 region, and higher identity with other strains of enterovirus group A (EV-A) in the P2 and P3 regions. Genetic recombination analysis revealed that the Jiangsu strains had three genetic recombination patterns with other EV-A epidemic strains in the P2, P3 and 3′-UTR regions. These recombination patterns took place during the sustained and widespread circulation of CVA4 in people and increased the transmissibility of CVA4.Conclusions:This study analyzes the phylogenetic and molecular features of 28 whole genomes of Jiangsu CVA4 strains, which helps to better understand the genomic diversity of CVA4. By analyzing the genetic recombination and amino acid mutations in the VP1 region, this study elucidates the evolution and transmission of CVA4, which is conducive to the control and prevention of CVA4 infection.

Objective:To analyze the epidemiological and clinical characteristics of respiratory syncytial virus (RSV) infection in children in Jiangsu Province from 2014 to 2023.Methods:The acute respiratory infection cases in children aged 0-14 years were selected from outpatient/emergency or inpatient departments in 2 surveillance sentinel hospitals, respectively, in Nanjing, Suzhou and Taizhou of Jiangsu from 1 July 2014 to 31 December 2023, and RSV nucleic acid test was conducted and the intensity of the RSV infection was accessed by WHO influenza epidemiological threshold method, and case information and clinical data were collected. χ2 test was used to compare the differences between groups, and the Bonferroni method was used for pairwise comparisons between groups. Results:In 4 946 cases of acute respiratory infections, the RSV positive rate was 8.21% (406/4 946), and the age M( Q1, Q3) of the cases was 1 (0, 3) years. The RSV positive rate was 10.92% (258/2 362) during 2014-2019 and 6.06% (118/1 948) during 2019-2023, the difference was significant ( χ2=31.74, P<0.001). RSV infection mainly occurred from October to March during 2014-2019, with the incidence peak in December and moderate or higher intensity. The seasonality of RSV infection was not obvious during 2019-2023, with low intensity. The RSV positive rate was highest in children in age group 0- years (17.85%, 151/846), and the positive rate declined gradually with age ( χ2=184.51, P<0.001). The RSV positive rate was higher in inpatient cases (9.84%, 244/2 480) than in outpatient/emergency cases (6.57%, 162/2 466) ( χ2=17.54, P<0.001). In the 155 RSV infection cases with complete clinical data, the clinical symptoms mainly included cough (99.35%, 154/155), fever (55.48%, 86/155), and shortness of breath (45.16%, 70/155). In the cases aged <6 months, the proportion of those with fever was low, but the proportion of those with shortness of breath, transferred to intensive care units, and receiving oxygen therapy were higher (all P<0.05). Children aged <6 months and those with underlying diseases were more likely to have severe RSV infection (all P<0.05). Conclusions:RSV infection in children in Jiangsu Province showed seasonal prevalence in winter from 2014 to 2019. Since 2020, the seasonal characteristics of the epidemic have changed, the epidemic period has been dispersed and the epidemic intensity has decreased. Infants <1 year old were at high risk for RSV infection, and those <6 months old and with underlying diseases might have severe infection.

Objective:To analyze the effects of SARS-CoV-2 infection and vaccination on virus mutation.Methods:The whole genome sequencing sequences of 2 659 local SARS-CoV-2 specimens from Jiangsu Province in 2023 were selected for analysis, and relevant information such as demographic and clinical characteristics were collected, and the effects of infection and vaccination on the genome-wide mutation rate and S gene′s selective pressure of the virus were analyzed by univariate and multivariate linear regression models.Results:The average age of these infected patients was 55.0 (31.0, 74.0) years, 1 150 cases (43.2%) in the age group of ≥60 years, 1 367 cases (51.4%) were males, 2 044 cases (76.9%) had a history of COVID-19 vaccination, and 1 629 cases (61.3%) had the first-time infection. The clinical symptoms of the infected patients were mainly mild, with a total of 2434 cases (91.5%), and 29 cases (1.1%) with severe symptoms or more. The average substitution rate of SARS-CoV-2 was 9.69 (9.38, 9.98)×10 -4 subs/site/year, and the dN/dS value of the S gene was 6.08 (5.56, 8.66), which was significantly greater than that of 1 ( P<0.001), indicating positive selection. The result of univariate and multivariate linear regression model analysis showed that the SARS-CoV-2 substitution rate was higher in those with vaccination history and reinfection, aged 20-30 years, ≥60 years, and the SARS-CoV-2 substitution rate was lower in males with moderate clinical symptoms and severe disease and above. Those with a history of vaccination and reinfection, aged 50-60 years old, ≥60 years old have smaller S gene dN/dS. Conclusions:Under the immune pressure exerted by vaccination and infection, the genome-wide mutation of SARS-COV-2 accelerated, but the non-synonymous mutation rate of the S gene decreased. The mechanism causing these phenomena needs further study.