探讨新型冠状病毒疾病(COVID-19)疫情暴发前、后，呼吸道感染住院患儿呼吸道病原体变化情况。

选择2019年1月至2021年12月，成都市第三人民医院诊治的1 576例呼吸道感染住院患儿为研究对象。根据入院时间，将其分为研究组(n＝771，入院时间为2020年1月1日至2021年12月31日，COVID-19疫情期内)与对照组(n＝805，入院时间为2019年1月1日至2019年12月31日，COVID-19疫情暴发前)。采用间接免疫荧光法，检测2组患儿血清中嗜肺军团菌血清1型(LP1)、肺炎支原体(MP)等呼吸道9种病原体免疫球蛋白(Ig)M抗体。采用χ²检验，对2组患儿，不同性别、年龄段及季节患儿的血清呼吸道病原体IgM阳性率进行统计学比较。本研究遵循的程序经成都市第三人民医院医学伦理委员会批准(审批文号：成都三院伦〔2022〕S-110号)。监护人对患儿的诊治均知情同意。

①本研究1 576例呼吸道感染患儿的血清呼吸道病原体IgM阳性率为53.2%(839/1 576)。2组患儿血清Q热立克次体(COX) IgM均呈阴性，研究组患儿血清LP1及肺炎衣原体(CP) IgM均呈阴性。2019—2021年，每年纳入本研究的呼吸道感染患儿均以单一感染为主，其病原体以MP为主。2019、2020、2021年纳入本研究患儿呼吸道感染病原体≥2种的混合感染率逐年下降(23.1%、13.1%、4.6%)，并且两两比较差异均有统计学意义(P<0.001)。②2019、2020及2021年纳入本研究呼吸道感染患儿中，血清呼吸道病原体IgM阳性率位居前3位的病原体分别依次为MP、乙型流感病毒(INFB)及副流感病毒(PIV)，MP、PIV及INFB，MP、PIV及INFB。研究组患儿血清MP、呼吸道合胞病毒(RSV)、腺病毒、甲型流感病毒(INFA)、INFB及总体病原体IgM阳性率均较对照组低，而血清PIV IgM阳性率则较对照组高，并且差异均有统计学意义(P<0.05)。③研究组男性患儿血清MP及总体病原体IgM阳性率均低于女性患儿，对照组男性患儿血清MP、PIV及总体病原体IgM阳性率均低于女性患儿，并且上述差异均有统计学意义(P<0.05)；研究组男性及女性患儿血清呼吸道总体病原体IgM阳性率，分别低于对照组同性别患儿(36.2% vs 55.6%，47.6% vs 76.1%)，并且差异均有统计学意义(χ²＝32.78、60.69，均为P<0.001)。④研究组4个年龄段(0~1岁，≥1~3岁，≥3~7岁，≥7~18岁)患儿血清MP、PIV及总体病原体IgM阳性率比较，以及对照组上述4个年龄段患儿血清LP1、MP、RSV、INFB、PIV及总体病原体IgM阳性率比较，差异均有统计学意义(P<0.05)；研究组≥1~3岁、≥3~7岁、≥7~18岁呼吸道感染患儿的血清呼吸道总体病原体IgM阳性率，均低于对照组同年龄段患儿，并且差异均有统计学意义(P<0.05)。⑤研究组患儿春、夏、秋、冬4个季节血清MP、INFB及总体病原体IgM阳性率比较，以及对照组患儿4个季节血清MP、RSV、INFB、PIV及总体病原体IgM阳性率比较，差异均有统计学意义(P<0.05)；研究组患儿春、夏、秋季血清呼吸道总体病原体IgM阳性率，均较对照组同季节低，并且差异均有统计学意义(P<0.001)，其中春季的血清总体病原体IgM阳性率降低最显著。

MP、INFB及PIV是本院住院患儿呼吸道感染的常见病原体；COVID-19疫情暴发前、后均以MP单一感染为主，疫情暴发后INFB感染有所减少，PIV感染有所增加。

To explore the changes of respiratory pathogens in hospitalized children with respiratory tract infection before and after outbreak of the coronavirus disease 2019 (COVID-19) epidemic.

From January 2019 to December 2021, a total of 1 576 hospitalized children with respiratory infections treated in the Third People′s Hospital of Chengdu were selected as research subjects. According to admission time, they were divided into study group (n=771, admission time was from January 1, 2020 to December 31, 2021, during COVID-19 epidemic period) and control group (n=805, admission time was from January 1 to December 31 in 2019, before outbreak of COVID-19 epidemic). Serum immunoglobulin (Ig)M antibodies of 9 respiratory pathogens such as Legionella pneumophila serotype 1 (LP1) and Mycoplasma pneumoniae (MP) in two groups of children were detected by indirect immunofluorescence method. Chi-square test was used to statistically compare the respiratory pathogen IgM positive rates in serum of children between 2 groups, between different genders, among different age groups and different seasons. This study was approved by the Medical Ethics Committee of the Third People′s Hospital of Chengdu (Approval No. Lun [2022] S-110, Chengdu Third Hospital). The guardians signed informed consent to the diagnosis and treatment of the children.

① In this study, the positive rate of IgM of respiratory pathogens in serum of 1 576 children with respiratory tract infections was 53.2% (839/1 576). There were negative of serum Coxiella burnetii (COX) IgM in two groups of children, and children in study group were negative of serum LP1 and Chlamydia pneumoniae (CP) IgM. From 2019 to 2021, the annual hospitalized children with respiratory infections included in this study were mainly single pathogen infections, and MP was the main pathogen. The mixed infection rates of ≥2 pathogens in respiratory tract annually decreased in 2019, 2020 and 2021 (23.1%, 13.1%, 4.6%), and the differences between pairwise comparisons were statistically significant (P<0.05). ②Among the children admitted for respiratory tract infections, the top three IgM positive rates in serum of respiratory pathogens were MP, influenza B virus (INFB) and parainfluenza virus (PIV) in 2019, MP, PIV and INFB in 2020, MP, PIV and INFB in 2021. The serum IgM positive rates of MP, syncytial respiratory virus (RSV), adenovirus, influenza A virus (INFA), INFB and total pathogens in study group were all lower, while the serum PIV IgM positivity rate was higher than those in control group, and the differences were statistically significant (P<0.05). ③In study group, the IgM positive rates of serum MP and total pathogens of male children were lower than those of female children, and in control group, the IgM positive rates of serum MP, PIV and total pathogens of male children were lower than those of female children, and all of the above differences were statistically significant (P<0.05). The serum IgM positive rate of respiratory total pathogens of male and female children in study group were lower than those of same gender in control group, respectively, and the differences were statistically significant (36.2% vs 55.6%, 47.6% vs 76.1%; χ²=32.78, 60.69; all were P<0.001). ④There were significant differences among 4 age groups (0-1 years old, ≥1-3 years old, ≥3-7 years old, ≥7-18 years old) of serum IgM positive rates of MP, PIV and total pathogens in study group, also LP1, MP, RSV, INFB, PIV and total pathogens among 4 age groups in control group (P<0.05). The serum IgM positive rate of respiratory total pathogens of ≥1-3 years old, ≥3-7 years old and ≥7-18 years old children in study group were lower than those of same age group in control group, and the differences were statistically significant (P<0.05). ⑤There were significant differences among 4 seasons of spring, summer, autumn and winter of serum IgM positive rates of MP, INFB and total pathogens in study group, also MP, RSV, INFB, PIV and total pathogens among 4 seasons in control group (P<0.05). The serum IgM positive rate of respiratory total pathogens of children in spring, summer and autumn in study group were lower than those of same season in control group, and the differences were statistically significant (P<0.001), among which the serum IgM positive rate of respiratory total pathogens was the most decreased in spring.

MP, INFB and PIV are common pathogens of respiratory infections in hospitalized children in our hospital; MP single infection was predominant both before and after outbreak of COVID-19 epidemic, INFB infection decreased and PIV infection increased after outbreak of epidemic.