Compromises in determination of Mycoplasma pneumoniae incidence

Due to non-pharmaceutical interventions against Covid-19, the incidence of Mycoplasma Pneumoniae infections dropped dramatically during the Covid-19 pandemic. 1 Following the pandemic, a delayed re-emergence of M. pneumonia infections was observed, occurring much later that the resurgence of other respiratory pathogens. 1Understanding the incidence of M. pneumoniae before, during, and after the pandemic can provide further insights into the immunity patterns of M. pneumoniae including herd immunity and longevity of protection. 1 However, studies informing on M. pneumoninae incidence should be interpretated in the light of the studied population, test activity as well as test accuracy.In this issue of The Lancet Regional Health -Europe, the study from Dungu and colleagues presents a population-based study of M.pneumonia incidence among children and adolescents in Denmark from 2016 to 2024.Covering a population of 1,152,000 children and adolescents and including 14,241 cases of M. pneumoniae, the study finds a threefold increase in M. pneumoniae infection incidence in 2023-2024 compared with the pre-Covid19 seasons, indicating an immune debt caused by the decline in M. pneumonia during the Covid19 pandemic. 2 The study provides a timely nationwide investigation of the incidence of M. pneumoniae infections in all Danish children and adolescents and includes all polymerase chain reaction (PCR) tests for M. pneumoniae conducted in primary and secondary care across Denmark. 2 In Denmark all microbiological test reports are systematically collected in the Danish Microbiology Database, 3 regardless of where the test is carried out, and each test result is linked to a unique personal identification number, enabling true nationwide monitoring of communicable diseases and linkage to patient outcomes.As a part of the Danish national surveillance program, the number PCR test positive patients with M. pneumoniae is monitored weekly based on data from this nationwide microbiology database. 4 Most M. pneumoniae infections in children are mild and are managed in an outpatient setting. 5 In Denmark, children with M. pneumoniae are mainly seen in primary care where testing is performed based on the