Description of a Current Outbreak of <em>Mycoplasma pneumoniae</em> in the United States

During the COVID-19 pandemic, a significant decline in Mycoplasma pneumoniae was observed. However, M. pneumoniae reemerged globally in 2023. Here we describe a current outbreak of M. pneumoniae infections in the United States (US). More than 287 million patient records from all 50 states in the US were reviewed to identify patients with a M. pneumoniae diagnosis between January 1, 2017, and September 30, 2024. A C-chart was created by calculating the mean and standard error (SE) of cases during the pre-COVID-19 pandemic period, with the upper control limit (UCL) set at 3 SE above the mean. The presence of an outbreak was defined as counts above the UCL. Cumulative excess cases were used to estimate the magnitude of the outbreak, and the fold increase was calculated. A US outbreak of M. pneumoniae began at the end of 2023, resulting in 9,708 excess cases corresponding to a 9.0-fold increase over the baseline UCL. The outbreak is ongoing and is affecting both children and adults, including patients with M. pneumoniae community-acquired pneumonia requiring hospitalization. The current US outbreak of M. pneumoniae has significant implications for the management of patients with respiratory infections during the current pneumonia season.