ObjectiveTo investigate the epidemiological and clinical characteristics of human bocavirus (HBoV) in hospitalized children with acute lower respiratory tract infection (ALRTI) at a single-center children’s hospital in Shanghai, thereby providing evidence for the diagnosis, treatment, and prevention of HBoV infection. MethodsA retrospective study was conducted on 19 537 hospitalized children with ALRTI at Shanghai Children’s Hospital from January 2021 to December 2023. Multiplex polymerase chain reaction (PCR) combined with capillary electrophoresis was used to detect HBoV and 12 other common respiratory viruses /atypical pathogens. The positive detection rate, demographic characteristics (sex, age), temporal distribution (year, season) of HBoV, as well as the clinical characteristics of severe and non-severe pneumonia were analyzed. ResultsThe overall HBoV-positive rate was 2.57% (503/19 537), with 59.44% (299/503) being single infections and 40.56% (204/503) being co-infections. The positive detection rate was significantly higher in boys than that in girls (2.78% vs 2.33%, χ²=3.88, P=0.049). The highest infection rate was observed in toddlers, followed by infants (χ²=379.57, P<0.001). The positive rate peaked in 2021 and reached its lowest point in 2023 (χ²=45.49, P<0.001), with epidemics mainly prevalent in summer and autumn. The main clinical symptoms were cough (90.06%, 453/503), fever (75.94%, 382/503), and wheezing (39.96%, 201/503). Children with severe pneumonia showed a higher incidence of wheezing compared with the non-severe group (P<0.001), while underlying diseases and co-infections had no significant association with disease severity (P>0.05). ConclusionHBoV was an important pathogen of ALRTI in children, predominantly affecting infants and toddlers, with higher susceptibility in boys and seasonal peaks in autumn and summer. The main clinical manifestations included cough, fever, and wheezing, with wheezing being more prevalent in children with severe pneumonia.

Objective:To investigate the clinical characteristics of children with severe human metapneumovirus (HMPV) infection and identify the risk factors associated with critical illness.Methods:A retrospective cohort study was conducted, enrolling 157 hospitalized children with severe HMPV infection, who tested positive for HMPV nucleic acid via PCR-capillary electrophoresis fragment analysis of nasopharyngeal secretions at Shanghai Children′s Hospital from January 2021 to December 2023.Clinical features, co-infections, treatment, and outcomes were collected. Based on the diagnostic criteria for severe HMPV infection, the patients were categorized into a critical illness group and a non-critical illness group. Intergroup comparisons were performed using the χ2 test or the Mann-Whitney U test. Multivariate Logistic regression analysis was employed to identify risk factors for critical HMPV infection and to establish a predictive model.The performance of the model was evaluated using receiver operating characteristic (ROC) curve analysis and calibration curves. Results:Among the 157 cases of severe HMPV infection, there were 67 males and 90 females, with an onset age of 39.0 (20.0, 55.5) months. Single-pathogen infection was observed in 125 cases (79.6%), while mixed infections accounted for 32 cases (20.4%).Severe pneumonia was diagnosed in 136 cases (86.6%).The predominant manifestations of severe HMPV infection included fever 152 cases (96.8%), cough 151 cases (96.2%), and wheezing 94 cases (59.9%).Sixty-eight patients (43.3%) required non-invasive respiratory support, 58 cases (36.9%) were admitted to the intensive care unit, and 22 cases (14.0%) underwent mechanical ventilation. Of the total, 149 cases (94.9%) were discharged with improvement, 8 cases (5.1%) were discharged against medical advice, and there were no fatal cases. The cohort was further stratified into a critical illness group 31 cases and a non-critical illness group 126 cases. Compared to the non-critical illness group, the critical illness group exhibited significantly higher rates of respiratory distress, lethargy, and intercostal retractions, along with a higher proportion of underlying comorbidities, and elevated levels of C-reactive protein and procalcitonin (all P<0.05).Conversely, albumin and hemoglobin levels were significantly lower in the critical illness group (both P<0.05). ROC curve analysis revealed that the optimal cutoff value for the duration of fever in predicting severe HMPV infection was 4.5 days.The multivariate binary Logistic regression analysis revealed that prolonged fever duration (>4.5 days) ( OR=28.00, 95% CI 5.09-153.93, P<0.001), anorexia ( OR=11.72, 95% CI 1.26-108.75, P=0.030), and immune dysfunction ( OR=36.71, 95% CI 1.55-867.31, P=0.026) were independent risk factors for severe HMPV infection. A predictive model for critical illness was constructed based on these independent risk factors. ROC curve analysis demonstrated excellent discriminative ability, with an area under the curve of 0.96 (95% CI 0.92-1.00, P<0.001). The optimal predictive probability threshold was 0.17, yielding a sensitivity of 0.93 and specificity of 0.92. The calibration curve closely approximated the ideal curve, indicating good model calibration ( P=0.157). Conclusions:Severe HMPV infection is predominantly observed as a single infection and is prone to progress to severe pneumonia, with fever, cough, and wheezing as the main clinical manifestations. A subset of cases progresses to critical illness, though the overall prognosis is favorable. Prolonged fever duration (>4.5 days), anorexia, and immune dysfunction were independent risk factors for critical illness.The risk prediction model constructed for pediatric critical HMPV infection demonstrated robust discriminative ability with excellent calibration.

Objective:To analyze the distribution and epidemiological characteristics of non-bacterial pathogens in hospitalized children with acute respiratory infections at a tertiary pediatric hospital in Shanghai during 2023.Methods:A retrospective study was conducted on 10 591 children with acute respiratory tract infections who were hospitalized in Shanghai Children's Hospital from January to December 2023. A multiplex PCR combined with capillary electrophoresis platform was used to detect 11 common non-bacterial respiratory pathogens（including viruses and atypical pathogens）. Statistical analysis was carried out using SPSS 29.0 software. Qualitative data were presented as numbers and percentages，and the Chi-square test was employed to make comparisons between groups，aiming to analyze the differences in the distribution of different pathogens according to gender，age group，and season. Additionally，based on the severity of the disease，patients were calssified into a severe pneumonia group and a non-severe pneumonia group to further explore the characteristics of the pathogen spectrum of severe pneumonia.Results:The total detection rate of pathogens was 54.39%（5 760/10 591），and the proportion of mixed infections was 12.76%（735/5 760）. The dominant pathogens and their proportions were as follows： Mycoplasma pneumoniae（19.20%，2 034/10 591），human rhinovirus（12.16%，1 288/10 591），influenza A virus（8.31%，880/10 591），and respiratory syncytial virus（8.14%，862/10 591）. Epidemiological characteristics showed that：（1）In terms of age： Mycoplasma pneumoniae was more common in older children（29.55%，901/3 049，in the school-age group，χ 2 = 653.67， P<0.001）. Influenza A virus had a high incidence in the adolescent group（11.34%，45/397，χ 2=48.69， P<0.001）. Respiratory syncytial virus was most susceptible in the infant group（20.94%，280/1 337，χ 2=739.92， P<0.001）. Human rhinovirus showed the characteristic of general susceptibility across all ages.（2）Monthly and seasonal distribution： Mycoplasma pneumoniae had a seasonal epidemic in summer and autumn（it began to rise in May and peaked in October at 34.22%，439/1 283）；influenza A virus had a bimodal distribution in spring and winter（the peak was 37.15% in March，315/848）；respiratory syncytial virus had a dominant epidemic in spring and summer（the detection rate was 21.24% in May，206/970），and human rhinovirus was prevalent throughout the year.（3）Clinical correlation：The detection rate of pathogens in the severe pneumonia group was significantly higher than that in the non-severe group：84.19%（426/506） vs 2.89%（5 334/10 085），χ 2=56.23， P<0.001. Conclusions:In 2023，the pathogen spectrum of hospitalized children with acute respiratory infections in the Shanghai area exhibits an epidemic pattern dominated by Mycoplasma pneumoniae，and its transmission dynamics are significantly age-dependent. This study delineates the pathogen-host-environment tripartite interactions，establishing an evidence-based foundation for formulating precision diagnostic-therapeutic algorithms and seasonal nosocomial infection prevention frameworks.

Objective:To analyze the distribution and epidemiological characteristics of non-bacterial pathogens in hospitalized children with acute respiratory infections at a tertiary pediatric hospital in Shanghai during 2023.Methods:A retrospective study was conducted on 10 591 children with acute respiratory tract infections who were hospitalized in Shanghai Children's Hospital from January to December 2023. A multiplex PCR combined with capillary electrophoresis platform was used to detect 11 common non-bacterial respiratory pathogens（including viruses and atypical pathogens）. Statistical analysis was carried out using SPSS 29.0 software. Qualitative data were presented as numbers and percentages，and the Chi-square test was employed to make comparisons between groups，aiming to analyze the differences in the distribution of different pathogens according to gender，age group，and season. Additionally，based on the severity of the disease，patients were calssified into a severe pneumonia group and a non-severe pneumonia group to further explore the characteristics of the pathogen spectrum of severe pneumonia.Results:The total detection rate of pathogens was 54.39%（5 760/10 591），and the proportion of mixed infections was 12.76%（735/5 760）. The dominant pathogens and their proportions were as follows： Mycoplasma pneumoniae（19.20%，2 034/10 591），human rhinovirus（12.16%，1 288/10 591），influenza A virus（8.31%，880/10 591），and respiratory syncytial virus（8.14%，862/10 591）. Epidemiological characteristics showed that：（1）In terms of age： Mycoplasma pneumoniae was more common in older children（29.55%，901/3 049，in the school-age group，χ 2 = 653.67， P<0.001）. Influenza A virus had a high incidence in the adolescent group（11.34%，45/397，χ 2=48.69， P<0.001）. Respiratory syncytial virus was most susceptible in the infant group（20.94%，280/1 337，χ 2=739.92， P<0.001）. Human rhinovirus showed the characteristic of general susceptibility across all ages.（2）Monthly and seasonal distribution： Mycoplasma pneumoniae had a seasonal epidemic in summer and autumn（it began to rise in May and peaked in October at 34.22%，439/1 283）；influenza A virus had a bimodal distribution in spring and winter（the peak was 37.15% in March，315/848）；respiratory syncytial virus had a dominant epidemic in spring and summer（the detection rate was 21.24% in May，206/970），and human rhinovirus was prevalent throughout the year.（3）Clinical correlation：The detection rate of pathogens in the severe pneumonia group was significantly higher than that in the non-severe group：84.19%（426/506） vs 2.89%（5 334/10 085），χ 2=56.23， P<0.001. Conclusions:In 2023，the pathogen spectrum of hospitalized children with acute respiratory infections in the Shanghai area exhibits an epidemic pattern dominated by Mycoplasma pneumoniae，and its transmission dynamics are significantly age-dependent. This study delineates the pathogen-host-environment tripartite interactions，establishing an evidence-based foundation for formulating precision diagnostic-therapeutic algorithms and seasonal nosocomial infection prevention frameworks.

Objective:To investigate the clinical characteristics of children with severe human metapneumovirus (HMPV) infection and identify the risk factors associated with critical illness.Methods:A retrospective cohort study was conducted, enrolling 157 hospitalized children with severe HMPV infection, who tested positive for HMPV nucleic acid via PCR-capillary electrophoresis fragment analysis of nasopharyngeal secretions at Shanghai Children′s Hospital from January 2021 to December 2023.Clinical features, co-infections, treatment, and outcomes were collected. Based on the diagnostic criteria for severe HMPV infection, the patients were categorized into a critical illness group and a non-critical illness group. Intergroup comparisons were performed using the χ2 test or the Mann-Whitney U test. Multivariate Logistic regression analysis was employed to identify risk factors for critical HMPV infection and to establish a predictive model.The performance of the model was evaluated using receiver operating characteristic (ROC) curve analysis and calibration curves. Results:Among the 157 cases of severe HMPV infection, there were 67 males and 90 females, with an onset age of 39.0 (20.0, 55.5) months. Single-pathogen infection was observed in 125 cases (79.6%), while mixed infections accounted for 32 cases (20.4%).Severe pneumonia was diagnosed in 136 cases (86.6%).The predominant manifestations of severe HMPV infection included fever 152 cases (96.8%), cough 151 cases (96.2%), and wheezing 94 cases (59.9%).Sixty-eight patients (43.3%) required non-invasive respiratory support, 58 cases (36.9%) were admitted to the intensive care unit, and 22 cases (14.0%) underwent mechanical ventilation. Of the total, 149 cases (94.9%) were discharged with improvement, 8 cases (5.1%) were discharged against medical advice, and there were no fatal cases. The cohort was further stratified into a critical illness group 31 cases and a non-critical illness group 126 cases. Compared to the non-critical illness group, the critical illness group exhibited significantly higher rates of respiratory distress, lethargy, and intercostal retractions, along with a higher proportion of underlying comorbidities, and elevated levels of C-reactive protein and procalcitonin (all P<0.05).Conversely, albumin and hemoglobin levels were significantly lower in the critical illness group (both P<0.05). ROC curve analysis revealed that the optimal cutoff value for the duration of fever in predicting severe HMPV infection was 4.5 days.The multivariate binary Logistic regression analysis revealed that prolonged fever duration (>4.5 days) ( OR=28.00, 95% CI 5.09-153.93, P<0.001), anorexia ( OR=11.72, 95% CI 1.26-108.75, P=0.030), and immune dysfunction ( OR=36.71, 95% CI 1.55-867.31, P=0.026) were independent risk factors for severe HMPV infection. A predictive model for critical illness was constructed based on these independent risk factors. ROC curve analysis demonstrated excellent discriminative ability, with an area under the curve of 0.96 (95% CI 0.92-1.00, P<0.001). The optimal predictive probability threshold was 0.17, yielding a sensitivity of 0.93 and specificity of 0.92. The calibration curve closely approximated the ideal curve, indicating good model calibration ( P=0.157). Conclusions:Severe HMPV infection is predominantly observed as a single infection and is prone to progress to severe pneumonia, with fever, cough, and wheezing as the main clinical manifestations. A subset of cases progresses to critical illness, though the overall prognosis is favorable. Prolonged fever duration (>4.5 days), anorexia, and immune dysfunction were independent risk factors for critical illness.The risk prediction model constructed for pediatric critical HMPV infection demonstrated robust discriminative ability with excellent calibration.

Objective:To investigate the impact of SARS-CoV-2 pandemic on the prevalence of viral pathogens in hospitalized children with acute respiratory tract infections (ARTIs) in Shanghai.Methods:A total of 6 020 throat swab specimens were collected from hospitalized children with ARTIs in Shanghai Children′s Hospital from August 1, 2019 to February 28, 2022. Eleven common respiratory pathogens were detected using multiplex PCR and capillary electrophoresis. Pre-epidemic data referred to the data from August to December, 2019, and the data from August to December, 2020 and August to December, 2021 were used as the post-epidemic data for comparison. Based on the data from March 2020 to February 2022 (the epidemic period), the epidemiology of respiratory pathogens in children with ARTIs in different seasons were compared (spring: March to May, summer: June to August, autumn: September to November, winter: December to February of the next year).Results:Of the 6 020 specimens obtained from the patients, 3 753 (62.34%) were positive for at least one pathogen. Human rhinovirus (HRV) was the most commonly detected pathogen (22.76%, 1 442/6 020), followed by human respiratory syncytial virus (HRSV) (16.05%, 966/6 020). From August to December, the detection rate of single respiratory pathogen was 87.94% (569/647) in 2019, 66.21% (480/725) in 2020 and 60.33% (1 075/1 782) in 2021, and the co-infection rate was 25.66% (166/647) in 2019, 9.93% (72/725) in 2020 and 8.87% (158/1 782) in 2021, showing a decreasing trend (χ 2=165.19 and 127.79, P<0.01). Compared with the pre-epidemic period, human metapneumovirus (HMPV), HRV and human parainfluenza virus (HPIV) were the most prevalent pathogens in 2020 [4.97%(36/725), 34.21%(248/725) and 14.48%(105/725); χ 2=26.16, 42.04 and 60.52; P<0.01] and HRSV was the predominant pathogen in 2021 [21.27%(387/1 782), χ 2=44.26, P<0.01]. During the epidemic period, the detection rate of pathogens was 64.49%(1 340/2 078) in 2020, which was significantly higher than that in 2021 [57.48%(1 771/3 081), χ 2=25.43, P<0.01]. Only two respiratory pathogens, Mycoplasma pneumonia and human coronavirus, were detected in the spring of 2020; HRV, human adenovirus and HPIV were detected since the summer of 2020; influenza virus B was detected since the spring of 2021; influenza virus A was detected in only one case in 2020 and other respiratory pathogens were detected since the autumn of 2020. HRV+ HRSV were the main pathogens of co-infections. Conclusions:A series of prevention and control measures taken after the SARS-CoV-2 epidemic caused major changes in the prevalence and the epidemiology of respiratory pathogens in hospitalized children in Shanghai. With the normalization of epidemic prevention and control, the cancellation of strict epidemic prevention policy might lead to the outbreak of some pathogens (HMPV, HRV, HPIV and HRSV) and much attention should be paid to the outbreaks of other respiratory pathogen infections in children.

Objective:To explore the correlation of EBV DNA load in two different types of plasma and peripheral blood mononuclear cells (PBMCs) in children with Epstein-Barr Virus (EBV) infection diseases.Methods:A retrospective evaluated was performed on EBV DNA quantification in plasma and PBMCs by qPCR between April, 2019 and December, 2020. The samples were collected from children of 456 cases with EBV infection and 2 306 healthy cases. In EBV infection group, boys were 253 and girls were 203, aged from 8 days to months to 16 years. In healthy group, boys were 1 267 and girls were 1 039, aged from 8 days to 16 years.Results:Infectious mononucleosis (IM) was the most common disease associated with EBV infection 73.68%(336/456). The detection rate of plasma and PBMCs in EBV infection group was 91.89% (419/456)and 99.34% (453/456)respectively, and was 100%(456/456) in plasma or PBMCs. The detection rate of plasma and PBMCs in healthy group was 1.13%(26/2 306) and 30.01%(715/2 306), respectively. Levels of EBV DNA in plasma and PBMCs in EBV infection group [IM, acute infections, pneumonia, post-transplantation lymphoproliferative disorder (PTLD), hemophagocytic lymphohistiocytosis, tonsillitis and lymphadenitis] was significantly higher than those in healthy group (In plasma, Z=-47.18,-34.41,-33.40,-31.71,-24.38,-20.86 and -20.59,respectively; In PBMCs, Z=-33.17,-16.45,-11.33,-9.45,-5.57,-5.16 and -5.45, respectively; P<0.05). In IM group, EBV DNA load in plasma and PBMCs in remission stage was significantly lower than those in infection stage ( Z=-11.45, -8.53; P<0.05). In PTLD group, there was significant difference in EBV DNA load in plasma between infection and remission stage ( Z=-4.13, P<0.05), while there was no significant difference in EBV DNA load in PBMCs ( Z=-0.817, P>0.05). Conclusions:EBV infection was mainly caused by IM. Combined detection of plasma and PBMCs in EBV DNA is valuable for improving diagnosis ability of EBV infection-related diseases, and the load of EBV DNA could be used as a marker.

Objective:To explore the correlation of EBV DNA load in two different types of plasma and peripheral blood mononuclear cells (PBMCs) in children with Epstein-Barr Virus (EBV) infection diseases.Methods:A retrospective evaluated was performed on EBV DNA quantification in plasma and PBMCs by qPCR between April, 2019 and December, 2020. The samples were collected from children of 456 cases with EBV infection and 2 306 healthy cases. In EBV infection group, boys were 253 and girls were 203, aged from 8 days to months to 16 years. In healthy group, boys were 1 267 and girls were 1 039, aged from 8 days to 16 years.Results:Infectious mononucleosis (IM) was the most common disease associated with EBV infection 73.68%(336/456). The detection rate of plasma and PBMCs in EBV infection group was 91.89% (419/456)and 99.34% (453/456)respectively, and was 100%(456/456) in plasma or PBMCs. The detection rate of plasma and PBMCs in healthy group was 1.13%(26/2 306) and 30.01%(715/2 306), respectively. Levels of EBV DNA in plasma and PBMCs in EBV infection group [IM, acute infections, pneumonia, post-transplantation lymphoproliferative disorder (PTLD), hemophagocytic lymphohistiocytosis, tonsillitis and lymphadenitis] was significantly higher than those in healthy group (In plasma, Z=-47.18,-34.41,-33.40,-31.71,-24.38,-20.86 and -20.59,respectively; In PBMCs, Z=-33.17,-16.45,-11.33,-9.45,-5.57,-5.16 and -5.45, respectively; P<0.05). In IM group, EBV DNA load in plasma and PBMCs in remission stage was significantly lower than those in infection stage ( Z=-11.45, -8.53; P<0.05). In PTLD group, there was significant difference in EBV DNA load in plasma between infection and remission stage ( Z=-4.13, P<0.05), while there was no significant difference in EBV DNA load in PBMCs ( Z=-0.817, P>0.05). Conclusions:EBV infection was mainly caused by IM. Combined detection of plasma and PBMCs in EBV DNA is valuable for improving diagnosis ability of EBV infection-related diseases, and the load of EBV DNA could be used as a marker.

Objective:To investigate the genetic characteristics of norovirus (NoV) in children with acute gastroenteritis in Shanghai.Methods:A total of 709 stool specimens were collected from outpatients with acute gastroenteritis in Children′s Hospital of Shanghai from October 2018 to September 2019. Real-time RT-PCR was used for qualitative detection of NoV, and RT-PCR was used to identify the genotypes of NoV with the primers of VP1 gene, RdRp region and RdRp-VP1 region. SPSS20.0 statistical software was used for data processing and bioinformatics software was used for homology, phylogenetic and recombination analysis of NoV gene sequences.Results:NoV was detected in 265 out of the 709 stool specimens with a positive rate of 37.4%. Sequence analysis of RdRp region and VP1 gene showed that seven different genotypes including GⅡ.P16-GⅡ.2, GⅡ.P12-GⅡ.3, GⅡ.Pe-GⅡ.4_Sydney 2012, GⅡ.P7-GⅡ.6, GⅡ.P8-GⅡ.8, GⅡ.P21-GⅡ.13 and GⅡ.P17-GⅡ.17 were detected from 111 NoV-positive specimens. The predominated genotype was GⅡ.P16-GⅡ.2 (30.6%, 34/111), followed by GⅡ.Pe-GⅡ.4_Sydney 2012 (27.0%, 30/111) and GⅡ.P12-GⅡ.3 (24.3%, 27/111). Two new NoV recombinant strains belonging to GⅡ.P21-GⅡ.13 genotype were identified and the recombination site was in the junction region of ORF1 and ORF2. NoV infection occurred every month, but the predominant genotype was different. No significant difference in the positive rates of NoV was found between male and female patients ( P=0.329). However, there were significant differences between different age groups ( P=0.011) and the children in the age groups of >11-12 years old and >2-3 years old had higher rates of NoV infection. Conclusions:The predominated recombinant NoV strains belonged to GⅡ.P16-GⅡ.2, GⅡ.Pe-GⅡ.4_Sydney 2012 and GⅡ.P12-GⅡ.3 genotypes, and two new recombinant NoV strains (GⅡ.P21-GⅡ.13) were found in Shanghai during October 2018 to September 2019. Gene sequencing across ORF1 and ORF2 was conducive to better understanding the NoV genotypes and recombination.

Objective To understand the mutations of macrolide resistance gene locus (23S rRNA) of Mycoplasma pneumoniae (MP) and its correlation with clinical features .Methods A total of 354 respiratory tract samples were collected from children pa-tients with pneumonia .MP and its mutations in 23S rRNA gene locus were detected by real-time PCR .The children cases of MP positive were divided into the mutation group and non-mutation group .Then the clinical data were compared between the two groups .Results Among 354 respiratory tract samples ,166 cases(46 .9% ) were MP positive ,moreover the mutation of 23S rRNA gene locus existed in 135 MP positive samples with the positive detection rate of 81 .3% ,while no 23S rRNA gene locus mutations were detected in 31 samples .Analyzing the clinical data of the mutation group and non-mutation group found that there was no sta-tistical difference in the aspects of age and gender between the two groups .The occurrence rates of severe pneumonia and extrapul-monary complications in the mutation group were higher than those in the non-mutation group (P<0 .05) ,moreover the average hospitalization time and fever duration in the mutation group were longer than those in the non-mutation group (P<0 .05) .Conclu-sion 23S rRNA gene locus mutation has higher detection rate ,prompting that MP shows high resistant rate to macrolides ,which could provide a certain basis for treatment of M P infections .