Mycoplasma pneumoniae Outbreak in 2023: Post-pandemic Resurgence of an Atypical Bacterial Pathogen

The syndromic nature of infections caused by pneumonia-causing pathogens including Mycoplasma pneumoniae necessitates detection via multiplex PCR for accurate and timely diagnosis to control the infection spread. In this study, we demonstrate an increase in the detection of M. pneumoniae in the outpatient population, during 2023, as compared to the previous two years (2021-2022). In this aggregated survey, respiratory samples collected within the continental United States were tested for the presence of M. pneumoniae and other respiratory bacterial and viral pathogens using a multiplex PCR assay. Patient data was analyzed on the basis of age, gender and geographical location. The positive detection of M. pneumoniae in 2021 and 2022 was 0.004% and 0.006%, respectively. The positivity rate of M. pneumoniae in 2023 increased to 0.21%. The highest proportion of M. pneumoniae cases were detected from Georgia with the outbreak generally concentrated in large urban settings. Median age of the patients testing positive for M. pneumoniae was 10 (interquartile range [IQR] 8-18) years with an almost equal distribution between male and female patients. Other respiratory, viral and bacterial, pathogens detected in samples positive for M. pneumoniae were similar in proportion to the M. pneumonia-negative population. A survey of the ICD-10 codes submitted in conjunction with the samples suggests that the current outbreak is mostly associated with upper respiratory tract infections. The present study is the first detailed report in the United States that shows an unprecedented increase in the detection of M. pneumoniae in the outpatient population during 2023. Our analysis suggests that this outbreak was not associated with any other bacterial or viral respiratory pathogen. The outbreak of this atypical pathogen was concentrated in the pediatric population in large urban areas. The 2023 outbreak could be a return of the cyclical M. pneumoniae outbreaks witnessed prior to the COVID-19 pandemic. Our study highlights the importance of performing continuous surveillance of respiratory pathogens, especially in the altered epidemiological landscape of the post-COVID world.