In recent years, data from CDC surveillance and paediatric clinics suggest that the prevalence of respiratory infections in children has changed compared with the past, that regional prevalence statistics are of directional significance for the diagnosis and treatment of respiratory infections in children, and that large sample analyses of the epidemiology of children's respiratory pathogens in the northeast region of Sichuan Province are still rare.

To ascertain the prevalence of 13 respiratory non-bacterial pathogens in children in three areas of northeastern Sichuan Province (Bazhong, Nanchong and Guang'an) following the outbreak, with a view to providing a basis for the prevention and treatment of respiratory infections in clinical children.

A retrospective analysis of pathogen samples from 15 772 children diagnosed with acute respiratory tract infections and hospitalised in Bazhong Central Hospital, Nanchong Central Hospital and Guang'an People's Hospital between 7 December 2022 and 30 June 2024 was conducted. Of these, 8 707 (55.2%) were male and 7 065 (44.8%) were female. The subjects were divided into four groups according to their age groups: infant group (<1 year old), 3 938 cases; toddler group (1-<3 years old), 6 434 cases; preschool group (3-<6 years old), 3 231 cases; and school-age group (6-14 years old), 2 169 cases. The onset of the disease was categorised according to the season, with 15 772 cases divided as follows: 5 423 cases in the spring (March to May), 2 594 cases in the summer (June to August), 3 121 cases in the autumn (September to November) and 4 634 cases in the winter (December to February). A total of 13 non-bacterial pathogens, including influenza A virus, influenza A virus H1N1, influenza A virus H3N2, influenza B virus, parainfluenza virus, Mycoplasma pneumoniae, chlamydia, parapneumovirus, respiratory syncytial virus, adenovirus, rhinovirus, bocavirus and coronavirus, were detected using the multiplex reverse transcription polymerase chain reaction technique. The subsequent investigation focused on the detection of pathogens in the total sample, with the positive detection rate of each pathogen being compared among different regions, genders, age groups and seasons.

Of the 15 772 respiratory samples, 11 618 (73.66%) were positive for pathogens, while 3 632 (23.03%) were identified as mixed infections. The most prevalent pathogens identified were rhinovirus (24.5%), respiratory syncytial virus (16.4%), Mycoplasma pneumoniae (13.8%), influenza A virus (9.4%) and parainfluenza virus (8.9%). The total detection rates of pathogens in samples from the Bazhong, Nanchong and Guang'an regions were 80.9%, 73.7%, and 75.3%, respectively. The difference in the total detection rates of pathogens in samples from the three regions was statistically significant when comparing the rates of pathogens in samples from the three regions (χ²=101.119, P<0.001). The total detection rate of pathogens in samples from boys (72.1%) was lower than that of girls (75.6%) (χ²=24.539, P<0.001). However, among the 13 pathogens, except for coronavirus, the differences in the detection rates were not statistically significant when compared among different genders (P>0.05). A statistically significant difference was observed when the total detection rates of pathogens in samples from the infant, toddler, preschool and school-age groups were compared (χ²=174.613, P<0.001). Among the 13 pathogens, with the exception of coronavirus, statistically significant differences were identified when the detection rates of the remaining pathogens were compared among different age groups (P<0.05). Furthermore, a comparison of the total detection rates of pathogens in samples collected during different seasons (spring, summer, autumn and winter) revealed a statistically significant difference (χ²=364.584, P<0.001). Notably, the winter samples exhibited the highest total detection rate of pathogens (80.0%), while the spring samples exhibited the lowest (72.3%) .

The main pathogens of acute respiratory infections in children in the three regions of northeast Sichuan were rhinovirus, respiratory syncytial virus, Mycoplasma pneumoniae, influenza A virus and parainfluenza virus, and the epidemiology varied by region. Among the 13 pathogens, except for coronaviruses, there was no difference in the detection rate among different genders but there were differences between age and seasonal subgroups.