Current Mycoplasma pneumoniae epidemic among children in Shanghai: unusual pneumonia caused by usual pathogen

Excerpt

Mycoplasma pneumoniae (M. pneumoniae), primarily transmitted through respiratory droplets when infected individuals cough or sneeze, is a common cause of community-acquired pneumonia, especially among school-age children and adolescents. The infection occurs endemically with an epidemic peak every few years. The worldwide incidence confirmed by direct test methods was reported to be 8.61% between 2017 and 2020 across all age groups [1]. During the coronavirus disease 2019 (COVID-19) pandemic, from 2020 to 2021, the incidence decreased to 1.69% due to nonpharmaceutical interventions (NPIs) [1]. Until 2022, despite the relaxation or discontinuation of NPIs, reductions in incidence continued to be seen in 20 countries across Europe, Asia, the Americas, and Oceania [2]. In China, there was initially a consistent trend in the number of patients with Mycoplasma pneumoniae pneumonia (MPP) both before and after the pandemic [3‐6]. After that, an unusually different pattern was observed starting in 2021. Typically, M. pneumoniae infection presents with symptoms of fever and cough, often accompanied by sore throat, coryza, and occasionally, headache [7]. From April 2020 to early December 2022, has been among the strictest, longest approaches to tackling the pandemic anywhere in the world. Such a long-term NPI has caused a potential for more severe respiratory pathogens epidemics due to a so-called immunity debt. With the lifting of NPI policy, China has experienced peaks in influenza viruses, respiratory syncytial virus (RSV), and M. pneumoniae over the past year. Notably, M. pneumoniae has undergone a prolonged non-seasonal epidemic, gaining prevalence from April and reaching its peak from October to November. The vast majority of the children, especially infants and preschool children, who have not been exposed to these respiratory pathogens, become a susceptible population that is so large that a sizable unseasonal outbreak occurs when a previously usual respiratory pathogen begins circulating. Therefore, the recently reported spike in respiratory illnesses, especially pneumonia in children is mostly caused by M. pneumoniae infection. Additionally, macrolide-resistant M. pneumoniae infection also complicates the clinical treatment of this MPP epidemic [8‐10]. …