Epidemiology of Mycoplasma pneumoniae in children with acute respiratory infections in Hangzhou during January 2021 to June 2023

Objectives Mycoplasma pneumoniae (MP) is known to be a common pathogen causing human respiratory infections. On December 7, 2022, the Chinese government announced 10 new measures of Prevention and Control of COVID-19, marking the onset of the post-COVID-19 era. This study aimed to investigate the epidemiological characteristics of Mycoplasma pneumoniae (MP) infections among children from January 2021 to June 2023. Methods Children with respiratory tract infection were enrolled in the study with fever and one or more respiratory symptoms. A serological diagnosis was confirmed with MP IgM antibodies. Results A total of 18,763 patients were enrolled, of whom 4,867 cases were MP-positive, resulting in a positivity rate of 25.9 %. The MP positivity rate increased annually, with 18.6 , 26.7, and 33.2 % in 2021, 2022, and 2023, respectively. The main disease type of MP infection was Mycoplasma pneumoniae pneumonia (MPP), with 74.0 , 87.8, and 86.4 % in 2021, 2022, and 2023, respectively. Higher positivity rates were concentrated in children aged 6 years and older, and the positivity rate in children under 1 year of age in 2023 is the largest increase among all age groups. Conclusions The positivity rate of MP increased significantly after the adjustment of COVID-19 prevention and control in China, and the most significant increase was seen in the infant group. Effective prevention and control measures should be implemented to reduce the prevalence of MP infection among children aged 6 years older and the infant group (<1 year).