Objective:To characterize the etiological and genetic features of pediatric influenza outbreaks in Changzhou between 2021 and 2024，with the goal of informing evidence-based prevention strategies and guiding effective management of influenza outbreaks in school settings.Methods:During the period of 2021 to 2024，throat swabs of influenza-like cases from school outbreaks in Changzhou were collected. These samples underwent real-time reverse transcription-polymerase chain reaction（RT-PCR）testing and virus isolation. Epidemiological data were integrated to conduct pathogenetic analysis. The HA genes of isolated strains were amplified and sequenced to perform genetic characterization.Results:Between 2021 and 2024，a total of 256 influenza outbreaks were reported in schools in Changzhou. A total of 3 201 specimens were collected，of which 2 245 were tested positive for influenza viruses，resulting in a positivity rate of 70.13%. The outbreak season was primarily concentrated from December to February each year，with settings predominantly distributed in primary schools（accounting for 73.83%）. The predominant epidemic strains were influenza A viruses，including 118 outbreaks caused by H1N1 and 104 by H3N2. A total of 74 influenza virus strains were successfully isolated from positive specimens，and sequencing of the hemagglutinin（HA）gene was completed. Phylogenetic analysis revealed that certain B/Victoria lineage strains（e.g.，B/Changzhou/01/2021）clustered closely with the vaccine strain B/Austria/3594/17（bootstrap support：99%）. Among influenza H1N1 strains，multiple isolates from 2023—2024 clustered within the same major branch as A/Victoria/4897/2022（bootstrap support：100%）. In contrast，the H3N2 strains exhibited a complex evolutionary pattern，showing variable genetic distances to vaccine strains from different years（e.g.，A/Massachusetts/18/2022，A/Darwin/6/2021）；some isolates were closely related to vaccine strains，while others were more distantly related and scattered across the phylogenetic tree.Conclusions:The influenza outbreak situation in schools was severe and has significant public health implications. Continuous surveillance is essential，and preventive strategies should be promptly adjusted based on the epidemiological and genetic characteristics of circulating strains.

Objective:To characterize the etiological and genetic features of pediatric influenza outbreaks in Changzhou between 2021 and 2024，with the goal of informing evidence-based prevention strategies and guiding effective management of influenza outbreaks in school settings.Methods:During the period of 2021 to 2024，throat swabs of influenza-like cases from school outbreaks in Changzhou were collected. These samples underwent real-time reverse transcription-polymerase chain reaction（RT-PCR）testing and virus isolation. Epidemiological data were integrated to conduct pathogenetic analysis. The HA genes of isolated strains were amplified and sequenced to perform genetic characterization.Results:Between 2021 and 2024，a total of 256 influenza outbreaks were reported in schools in Changzhou. A total of 3 201 specimens were collected，of which 2 245 were tested positive for influenza viruses，resulting in a positivity rate of 70.13%. The outbreak season was primarily concentrated from December to February each year，with settings predominantly distributed in primary schools（accounting for 73.83%）. The predominant epidemic strains were influenza A viruses，including 118 outbreaks caused by H1N1 and 104 by H3N2. A total of 74 influenza virus strains were successfully isolated from positive specimens，and sequencing of the hemagglutinin（HA）gene was completed. Phylogenetic analysis revealed that certain B/Victoria lineage strains（e.g.，B/Changzhou/01/2021）clustered closely with the vaccine strain B/Austria/3594/17（bootstrap support：99%）. Among influenza H1N1 strains，multiple isolates from 2023—2024 clustered within the same major branch as A/Victoria/4897/2022（bootstrap support：100%）. In contrast，the H3N2 strains exhibited a complex evolutionary pattern，showing variable genetic distances to vaccine strains from different years（e.g.，A/Massachusetts/18/2022，A/Darwin/6/2021）；some isolates were closely related to vaccine strains，while others were more distantly related and scattered across the phylogenetic tree.Conclusions:The influenza outbreak situation in schools was severe and has significant public health implications. Continuous surveillance is essential，and preventive strategies should be promptly adjusted based on the epidemiological and genetic characteristics of circulating strains.

Objective: To analyze the epidemiological characteristics and genetic characteristics of sapovirus (SaV) in a cluster of schools in Changzhou, so as to provide a reference for the treatment of clustered vomiting and diarrhea events in schools. Methods: The epidemiological data and laboratory test data of sapovirus clusters in Changzhou from 2019 to 2022 were collected and analyzed. Partial VP1 genes of SaV positive samples were amplified and sequenced for phylogenetic analysis. Results: A total of 8 cases of clusters of SaV epidemics were reported in Changzhou City from 2019 to 2022, with 118 reported cases. The total attack rate was 1.47%, and the median of the attack number was 15. There were 6 outbreaks in kindergartens and 2 outbreaks in primary schools, which were reported in the epidemic period from September to December. The main clinical manifestations were vomiting (113 cases, 95.76 %), abdominal pain (39 cases, 33.05%), and diarrhea (16 cases, 13.56%). Among the 8 outbreaks, 17 sample strains were successfully sequenced. 5 outbreaks were GII.3 , and the other 3 outbreaks were GI.1, GI .3 and GII.2. GI and GII were the main genotypes in this area, and GII .3 was the predominant strain. Conclusion SaV is an important pathogen in the clusters of vomiting and diarrhea in schools after the transmission of norovirus. Continuous surveillance of SaV should be carried out to further understand its epidemiological characteristics and genotype distribution, so as to provide scientific basis for the prevention and control of the epidemic in schools.

Objective To analyze serotype distribution, drug resistance, quinolone resistance gene carrying status and genetic relationship of foodborne Salmonella and human Salmonella isolates in Changzhou from 2012 to 2018, to provide scientific basis for the prevention and control of Salmonella. Methods The serum type was identified by serum agglutination and liquid chip. The antibiotic sensitivity was determined by micro broth dilution method. The quinolone antibiotic resistance gene was determined by gene sequencing method. The multilocus sequence typing ( MLST ) typing was performed on quinolone-resistant Salmonella, and the genetic relationship was analyzed by BioNumerics 8.0. Results A total of 10 and 36 serotypes were detected in 46 foodborne Salmonella strains and 152 human Salmonella strains, respectively. The dominant serotypes were Indiana Salmonella and Salmonella typhimurium. Erythromycin resistance rate was the highest in both Salmonella strains, and the proportion of multidrug-resistant bacteria was 93.47 % ( 43 / 46 ) and 80.92 % ( 123 / 152 ), respectively. 38 strains of quinolone-resistant foodborne Salmonella GyrA subunit mainly occurred double mutations Asp87Asn, Ser83Phe, ParC subunit mainly occurred single mutation Ser80Arg, 119 strains of quinolone-resistant human Salmonella qnrS gene detection rate was higher, reached 68.1 % ( 81 / 119 ) ; The dominant ST types of quinolone-resistant Salmonella from two sources were ST17 and ST19, respectively. Conclusions The antibiotic sensitivity of the two Salmonella resistant strains from Changzhou was the same ; Synergistic drug resistance, but both quinolone resistance genemutations and carry inconsistent ; The ST type distribution of quinolone resistant strains isalso inconsistent, and the genetic relationship is far. It is suggested that the probability of Salmonella resistant bacteria infection caused by food transmission in our region is small, and the treatment of the two should be differentiated.

Objective To probe into the feasibility and applicability of the foodborne food risk monitoring and sentinel hospital foodborne disease surveillance on the Salmonella serotype identification by liquid phase suspension array. Methods The serotyping of Salmonella isolates was performed by traditional glass agglutination test. Meanwhile, the liquid phase suspension array was operated to analyze the antigen O, H and AT for classification identification. Results From 2012 to 2019, a total of 215 strains of Salmonella were collected divided into 38 serotypes, 96% of them could be analyzed by SSA kit. The results of xMAP were in accordance with the traditional agglutination. 8 of the 11 strains which cannot be checked out by glass agglutination seemed to be easy detected by liquid phase suspension array. Conclusion The liquid phase suspension array has advantages of high throughput, high sensitivity and high specificity. It is able to detect the Salmonella serotype rapidly during a short time. Compared with the traditional serum agglutination method, the liquid phase suspension array has obvious advantages in detection time. It can be useful and important in the break out of foodborne disease caused by Salmonella spp.

Objective To understand the epidemiological characteristics and variation of H3N2 influenza virus hemagglutinin (HA) gene in Changzhou from 2017 to 2018. Methods Throat swab specimens of the influenza-like cases were collected from Changzhou Influenza Monitoring Sentinel Hospital from April 2017 to March 2018. RNA was extracted from the specimens for influenza diagnosing and genotyping using real-time RT-PCR．H3N2 positive samples were isolated, and extracted RNA was used for amplification, sequencing and phylogenetic analysis of HA gene. Results From April 2017 to March 2018, 28 strains of influenza A (H3N2) virus were isolated. After gene sequencing, a phylogenetic tree was constructed. It was found that all of the strains belonged to Group3C.2a, which was similar to the vaccine strain A/Hong Kong/4801/2014. The HA amino acid sequence difference was analyzed and compared between the H3N2 influenza virus strains isolated in Changzhou and the vaccine strain A/Hong Kong/4801/2014. It was found that the epidemic strain isolated in Changzhou was in the HA epitope (A-E) region. Ten amino acid site mutations in the HA epitope (A-E) region and two amino acid site mutations in the stem region of HA antigen were found. Conclusion From April 2017 to March 2018, the influenza virus H3N2 prevalent in Changzhou was distributed on the same evolutionary branch with the vaccine strain A/Hong Kong/4801/2014 (group 3C.2a), rendering the popular trend of one subgroup. However, some amino acid sites of the HA epitope had variations, suggesting that mutations may occur, which may affect the immune effect of the vaccine. Monitoring needs to be strengthened in the future work.