Objective:To analyze the disease burden of respiratory syncytial virus (RSV)- associated lower respiratory tract infection (LRTI) in Chinese children under one year of age from 1990 to 2021.Methods:Using the Global Burden of Disease (GBD) 2021 database ( https://vizhub.healthdata.org/gbd-results/), we calculated deaths, mortality, age-standardized mortality rates (ASMR), disability- adjusted life years (DALYs), DALY rates, and age-standardized DALY rates (ASDR) to assess the disease burden of RSV-associated LRTI in Chinese children under one year of age. Joinpoint regression modeling was employed to analyze temporal trends in disease burden in China from 1990 to 2021, with stratification by time, age, and sex. Comparisons were made with global and high socio-demographic index (SDI) regions. Results:In 2021, there were 324 deaths (95% UI: 179-539) from RSV-LRTI in Chinese infants under one year of age, with a mortality rate of 2.82 per 100 000 (95% UI: 1.55-4.69), ASMR of 0.10 per 100 000 (95% UI: 0.06-0.16), DALYs of 29 131.28 years (95% UI: 16 050.27-48 398.30), DALY rate of 253.56 per 100 000 (95% UI: 139.70-421.26), and ASDR of 6.70 per 100 000 (95% UI: 3.72-11.12). All metrics were lower than global levels but significantly higher than high-SDI regions. From 1990 to 2021, substantial reductions were observed in deaths, mortality rates, DALYs, and DALY rates of RSV-LRTI among children under one year of age in China, globally, and in high-SDI regions. China achieved ASMR and ASDR reductions of－95.91% (95% CI:－97.75% to－92.96%) and－96.70% (95% CI:－98.19% to－94.33%), comparable to high-SDI regions but exceeding global averages. Joinpoint analysis showed average annual percentage changes (AAPC) in ASMR of－9.80% (95% CI:－10.45% to－9.14%) for China,－5.38% (95% CI:－5.83% to－4.91%) globally, and－7.13% (95% CI:－9.07% to－5.14%) for high-SDI regions (all P<0.001). The AAPC for ASDR were－10.41% (95% CI:－11.01% to－9.79%),－5.40% (95% CI:－5.82% to－4.97%), and－7.09% (95% CI:－9.70% to－4.41%) for China, the global average, and high-SDI regions, respectively, with the most pronounced decline occurring between 2019 and 2021 (ASMR decreased by 53.33%, 45.81%, and 61.31%, while ASDR declined by 52.50%, 44.54%, and 58.88% in China, globally, and in high-SDI regions, respectively). In 2021, both China and high-SDI regions exhibited declining mortality and DALY rates for RSV-LRTI with increasing age among children under one year, while neonates younger than 28 days consistently demonstrated the highest burden metrics. The rate of decline was comparable between China and high-SDI regions, with both exceeding the global average. Furthermore, from 1990 to 2021, male infants under one year of age in China, globally, and in high-SDI regions consistently showed higher overall trends in deaths, mortality rates, DALY, and DALY rates for RSV-LRTI compared to female infants. Conclusions:Although China's RSV-LRTI disease burden in infants under one year remains lower than global levels but higher than high-SDI regions, the country achieved reduction rates comparable to high-SDI regions, exceeding global averages. RSV-LRTI continue to pose significant health threats to neonates and male infants, necessitating age-specific and sex-specific prevention strategies.

Objective:To analyze the disease burden of respiratory syncytial virus (RSV)- associated lower respiratory tract infection (LRTI) in Chinese children under one year of age from 1990 to 2021.Methods:Using the Global Burden of Disease (GBD) 2021 database ( https://vizhub.healthdata.org/gbd-results/), we calculated deaths, mortality, age-standardized mortality rates (ASMR), disability- adjusted life years (DALYs), DALY rates, and age-standardized DALY rates (ASDR) to assess the disease burden of RSV-associated LRTI in Chinese children under one year of age. Joinpoint regression modeling was employed to analyze temporal trends in disease burden in China from 1990 to 2021, with stratification by time, age, and sex. Comparisons were made with global and high socio-demographic index (SDI) regions. Results:In 2021, there were 324 deaths (95% UI: 179-539) from RSV-LRTI in Chinese infants under one year of age, with a mortality rate of 2.82 per 100 000 (95% UI: 1.55-4.69), ASMR of 0.10 per 100 000 (95% UI: 0.06-0.16), DALYs of 29 131.28 years (95% UI: 16 050.27-48 398.30), DALY rate of 253.56 per 100 000 (95% UI: 139.70-421.26), and ASDR of 6.70 per 100 000 (95% UI: 3.72-11.12). All metrics were lower than global levels but significantly higher than high-SDI regions. From 1990 to 2021, substantial reductions were observed in deaths, mortality rates, DALYs, and DALY rates of RSV-LRTI among children under one year of age in China, globally, and in high-SDI regions. China achieved ASMR and ASDR reductions of－95.91% (95% CI:－97.75% to－92.96%) and－96.70% (95% CI:－98.19% to－94.33%), comparable to high-SDI regions but exceeding global averages. Joinpoint analysis showed average annual percentage changes (AAPC) in ASMR of－9.80% (95% CI:－10.45% to－9.14%) for China,－5.38% (95% CI:－5.83% to－4.91%) globally, and－7.13% (95% CI:－9.07% to－5.14%) for high-SDI regions (all P<0.001). The AAPC for ASDR were－10.41% (95% CI:－11.01% to－9.79%),－5.40% (95% CI:－5.82% to－4.97%), and－7.09% (95% CI:－9.70% to－4.41%) for China, the global average, and high-SDI regions, respectively, with the most pronounced decline occurring between 2019 and 2021 (ASMR decreased by 53.33%, 45.81%, and 61.31%, while ASDR declined by 52.50%, 44.54%, and 58.88% in China, globally, and in high-SDI regions, respectively). In 2021, both China and high-SDI regions exhibited declining mortality and DALY rates for RSV-LRTI with increasing age among children under one year, while neonates younger than 28 days consistently demonstrated the highest burden metrics. The rate of decline was comparable between China and high-SDI regions, with both exceeding the global average. Furthermore, from 1990 to 2021, male infants under one year of age in China, globally, and in high-SDI regions consistently showed higher overall trends in deaths, mortality rates, DALY, and DALY rates for RSV-LRTI compared to female infants. Conclusions:Although China's RSV-LRTI disease burden in infants under one year remains lower than global levels but higher than high-SDI regions, the country achieved reduction rates comparable to high-SDI regions, exceeding global averages. RSV-LRTI continue to pose significant health threats to neonates and male infants, necessitating age-specific and sex-specific prevention strategies.

Objective To investigate the influences of exposure to different environmental microbes on early-life gut microbiota colonization in mice.Methods Male (n=8) and female (n=16) adult specific pathogen free (SPF) BALB/c mice were caged together at a ratio of 2:l.After conception,the mice were divided into four groups according to the environments where the offsprings were reared at three different periods (fetal period,breastfeeding period and childhood).Group A:Offsprings were kept in a SPF environment throughout the study;group B:SPF environment during fetal and breastfeeding periods,and then ordinary environment during childhood;group C:SPF environment during fetal period,and then ordinary environment during breastfeeding period and childhood;group D:ordinary environment all the time.Fecal samples were collected at the end of week 3 and 5.Total bacterial DNA was extracted from each sample and analyzed by high throughput analysis.Kruskal-Wallis and Dunn-Bonferroni test were applied for statistical anaysis.Results 1.At the end of three weeks:(1) Diversity:① Phylum level:There were significant differences in the abundance of Firmicutes,Verrucomicrobia,Proteobacteria and Actinobacteria among the four group (all P＜0.01).Compared with group C and D,group A and B showed significantly decreased abundance of Firmicutes [30.876(23.448-41.218)× 10-2,3.317(1.116-4.641) 10-2 vs 71.936(53.587-86.713)× 10-2,79.105(56.305-82.736)× 10-2],but increased abundance of Verrucomicrobia and Proteobacteria [Verrucomicrobia:17.249(9.748-35.106)× 10-2,58.883(0.017-6.047)× 10-2 vs 0.152(0.066-1.890)× 10-2,0.003(0.000-0.016)× 10-2;Proteobacteria:12.640(0.336-15.070)× 10-2,3.653(3.362-4.5955)× 10-2 vs 0.219(0.134-0.325)× 10-2,0.124(0.116-0.165) × 10-2,all P＜0.05 or 0.01].② Genus level:There were significant differences in the abundance of Lactobacillus,Akkermansia and Bacteroides among the four groups (all P＜0.01).Compared with group C and D,group A and B showed significantly decreased abundance of Lactobacillus [19.283(8.618-31.541)× 10-2,0.339(0.264-22.278) × 10-2 vs 58.414(34.874-71.942)× 10-2,66.007(55.141-76.940)× 10-2],but increased abundance of Akkermansia,Bacteroides and Klebsiella [Akkermansia:17.247(9.748-35.106)× 10-2,58.883(0.017-60.475)× 10-2 vs 0.152(0.066-1.890)× 10-2,0.003(0.000-0.017)× 10-2;Bacteroides:3.978(0.683-25.171)× 10-2,8.216(6.023-9.946)× 10-2 vs 0.141(0.061-0.281)× 10-2,0.568(0.149-1.455)× 10-2;Klebsiella:0.209(0.050-8.888)× 10-2,1.402(0.865-1.692)× 10-2 vs 0.003(0.000-0.039) 10-2,0.000(0.000 0.001)× 10-2,all P＜0.05 or 0.01].(2) Alpha diversity:Significant differences were found in operational taxonomic unit (OTU) and Chaol index (P＜0.05),but not in Shannon index among the four groups (P＞0.05).The OTUs of group A and B were significantly lower than that of group D [246(221-348),257(209-280) vs 387(324-478),P=0.045 and 0.008,respectively].2.At the end of five weeks:(1) Diversity:① Phylum level:There were significant differences in the abundance of Firmicutes,Verrucomicrobia and Proteobacteria among the four groups (P＜0.05 or 0.01).The abundance of Firmicutes in gut microbiota in group A was lower than that in group B,C and D [13.765(64.181-24.238)× 10-2 vs 48.912(37.280-59.466)× 10-2,86.065(50.149-89.856) × 10-2,53.847(31.946-72.936) × 10-2],while that of Verrucomicrobia was higher [58.089(22.459-61.285)× 10-2 vs 0.001(0.000-0.005)× 10-2,0.000(0.000-0.001)× 10-2,0.003(0.000-0.006)× 10-2],all P＜0.05 or 0.01.② Genus level:There were significant differences in the abundance of Lactobacillus and Akkermansia among the four groups (P＜0.01).The abundance of Lactobacillus in gut microbiota in group A was lower than that in group B,C and D[1.755(0.805-8.833)× 10-2 vs 26.391(17.550-37.265)× 10-2,70.688(45.713-77.953) × 10-2,28.675 (15.660-57.224) × 10-2],while that of Akkermansia was higher [58.089(22.460-61.285)× 10-2 vs 0.000(0.000-0.006)× 10-2,0.000(0.000-0.001)× 10-2,0.003(0.000-0.006)× 10-2,all P＜0.05 or 0.01].(2) Alpha diversity:There were significant differences in OTU,Chaol and Shannon index among the four groups (P＜0.05 or 0.01).The OTU of group A was lower than that of group B,C and D [268(241-410) vs 438(380-516),562(533-588),546(473-599)],and the OTU,Chaol and Shannon index of group B were all lower than those of group C and D [OTU:438(380-516) vs 562(533-588),546(473-599);Chaol index:1 033(883-1 181) vs 1 285(1 220-1 338),1 328(1 155-1 516);Shannon index:3.85(3.25-4.50) vs 4.28(3.30-5.11),4.17(3.62-4.38),all P＜0.05 or 0.01].Conclusions Early-life exposure to different environments has an obvious impact on the diversity and composition of intestinal microbiota in mice.The less clean the living environment is,the more diverse the gut microflora will be.Furthermore,the window of opportunity for gut microbiota colonization seems to be related to breastfeeding period.