Background During the COVID-19 pandemic, we continuously monitored the epidemiology of influenza virus among pediatric patients from January 2021 to December 2023 in Hainan Island, China. Methods In this study, we collected 54,974 nasopharyngeal swab samples for IAV testing and 53,151 samples for IBV testing from pediatric outpatients. Additionally, we also collected 19,687 nasopharyngeal swab samples from pediatric inpatients for IAV and IBV testing. Outpatient samples were screened for IVs infection by the colloidal gold method. Targeted Next-Generation Sequencing (tNGS) was used to detect Influenza virus infections in inpatients. Influenza virus types were identified by analyzing the HA/NA partial regions. Results The findings revealed a decrease in the infection rate of IBV over the specified period, while the infection rate of IAV exhibited a rising trend. Additionally, B/Victoria lineage was the dominant epidemic strain in 2021, while the epidemic strains in 2022 and 2023 underwent a dynamic transformation from A/H3N2 to A/H1N1. Phylogenetic analysis revealed close relationships among the circulating strains. Nonetheless, because the sample size is limited, additional research is required. Conclusion Our findings suggest that the predominant types of influenza viruses in the pediatric population are dynamically changing, and non-pharmaceutical intervention measures can significantly impact the infection rate of influenza.

Background:COVID-19 has become a global epidemic, close contacts and asymptomatic patients are worthy of attention. Methods:A total of 1844 people in close contact with 76 COVID-19 patients were investigated, and nasopharyngeal swabs and venous blood were collected for centralized medical quarantine observation. Real-time fluorescence used to detect 2019-nCoV nucleic acid in nasopharyngeal swabs of all close contacts, and colloidal gold method used to detect serum specific antibodies. Levels of IgM and IgG specific antibodies were detected quantitatively through chemiluminescence from the first nucleic acid negative date (0 wk) within weekly periods of:1, 1-2, 2-3, and 6-7 weeks. Results:The total positive rate of the colloidal gold method (88.5%,23/26) was significantly higher (χ2=59.182,P< 0.001) than that of the healthy control group (2.0%, 1/50). There was significant difference in IgG concentration at different time points (0-7week) after nucleic acid turned negative (χ2=14.034,P=0.029). Serum IgG levels were significantly higher within weekly timepoints 4-5 wk(Z=-2.399, P=0.016), 5-6 wk(Z=-2.049,P=0.040), and 6-7 wk(Z=-2.197,P=0.028), compared to 1-2 wk after nucleic acid negative conversion. However, there was no significant difference (χ2=4.936,P=0.552) in IgM concentration between timepoints tested (0-7 weeks) after nucleic acid conversion. The positive rates of IgM and IgG in asymptomatic patients (χ2=84.660,P<0.001) were significantly higher than the controls (χ2=9.201,P=0.002) within 7 weeks of nucleic acid negative conversion. Conclusions: The IgG concentration in asymptomatic cases remained at a high level after nucleic acid turned negative. Nucleic acid combined with IgM and IgG antibody detection is a more effective way to screen asymptomatic infections.

Background: The situation of the corona virus disease 2019(COVID-19) continues to evolve, our study explored the significance of serum levels of Matrix Metalloproteinase 3 (MMP3) as a marker for patients with COVID-19. Methods: Sixty-two COVID-19 patients in the First Hospital of Hunan University of Chinese Medicine and Loudi Center for Diseases Prevention and Control, from January to March 2020, were sampled as the novel coronavirus pneumonia infected group. One hundred and thirty-one cases from the First Hospital of Hunan University of Chinese Medicine, including 67 healthy individuals and 64 non- COVID-19 inpatients, served as the non-infected group. Approximately every 5 d, sera from 20 cases were collected and analyzed thrice, using an automatic biochemical analyzer, to detect serum MMP3 concentrations. Following normality tests, differences in serum MMP3 levels between the infected and non-infected group were analyzed via SPSS (version 25.0) software, using the Wilcoxon rank sum test. Results: The MMP3 concentration was 44.44（23.46~72.12）ng/ml in the infected group and 32.42 (28.16~41.21）ng/ml in the non-infected group. The difference between the two groups was statistically significant (Z=-2.799, P=0.005<0.05). Serum MMP3 concentration, measured over three separate time points, were 55.98 (30.80~75.97) ng/ml, 34.84 (0.00~51.84) ng/ml, and 5.71 (0.00~40.46) ng/ml, respectively. Conclusion: Detection of serum MMP3 levels may play an important role in the development of therapeutic approaches for COVID-19 and may indicate the severity of disease.