Epidemiological Characteristics and Antimicrobial Resistance Profiles of Haemophilus influenzae Respiratory Infections in Hospitalized Children: A 7-Year Retrospective Study in Kunming

Abstract Objective To analyze age, sex, temporal patterns, co-detected pathogens and sputum-culture antimicrobial resistance of Haemophilus influenzae (Hi) respiratory infections among hospitalized children in Kunming from 2019 to 2025, so as to provide evidence for local prevention, control and rational selection of antimicrobial agents. Methods This retrospective study included hospitalized children diagnosed with Hi respiratory tract infection. We stratified and summarized epidemiological characteristics, co-infecting pathogens and antimicrobial susceptibility results of sputum isolates according to age group, month, season and gender. Results A total of 11,217 cases were confirmed by sputum culture or PCR. Annual case numbers fluctuated and increased overall, reaching the lowest level in 2020 and the highest in 2024–2025, with obvious concentration in winter and spring. The proportion of preschool and school-aged children gradually increased, whereas that of infants declined significantly (P < 0.001). Although boys were still predominant, the proportion of girls rose year by year. Common co-detected pathogens covered Streptococcus pneumoniae , respiratory syncytial virus, parainfluenza virus, rhinovirus, adenovirus and Mycoplasma pneumoniae , and co-detection patterns varied remarkably by year, season and age. Ampicillin, trimethoprim-sulfamethoxazole and cefaclor showed high resistance, while ceftriaxone, cefotaxime, rifampicin, meropenem and quinolones kept good activity. Conclusions Paediatric Hi respiratory infections present a winter-spring bimodal epidemic and an age shift toward older children. Third-generation cephalosporins are recommended as first-line empirical therapy. Continuous local surveillance and susceptibility data should guide clinical antibiotic use.