# Post-pandemic resurgence of Mycoplasma pneumoniae in coastal China: from seasonal waves to sustained transmission and expanded age susceptibility

## TL;DR

This study tracks a resurgence of Mycoplasma pneumoniae in coastal China after the pandemic, showing increased transmission and infection in younger children.

## Contribution

The study reveals a post-pandemic shift in Mycoplasma pneumoniae transmission patterns and age susceptibility in coastal China.

## Key findings

- MP positivity increased from 28.3% to 37.5% in two years, showing a post-pandemic resurgence.
- MP infections expanded to younger children, with a broadened age distribution.
- MP co-detections increased, especially with human adenovirus, linked to community virus circulation.

## Abstract

Mycoplasma pneumoniae (MP) represents a primary etiological agent of pediatric Acute Respiratory Infections (ARIs) in China. However, the epidemiological landscape of MP in coastal regions during the post-COVID-19 era remains poorly characterized. Here, we delineate the epidemiological dynamics of MP—including trends, seasonality, age-specific distribution, and viral co-detection patterns—among children with ARIs in the coastal city of Putian, Southeast China.

We retrospectively analyzed a cohort of 10,193 pediatric patients hospitalized with ARIs between December 2022 and November 2024. Oropharyngeal swabs from this cohort were assayed for MP and a panel of other respiratory pathogens using a multiplex reverse transcription-polymerase chain reaction (RT-PCR) platform. Data were stratified by time, season, and age to delineate the epidemiological characteristics of MP positivity.

Across the surveillance period (Dec 2022–Nov 2024), the overall MP positivity rate was 33.7% (3,437/10,193), with a significant increase from 28.3% in the first year to 37.5% in the second (P < 0.001), signaling a major post-pandemic resurgence. The epidemic pattern shifted from a discrete seasonal wave in the first year to a sustained, high-level plateau of transmission in the second. While school-age children consistently exhibited the highest positivity rates (59.1%), the age distribution of MP cases broadened significantly to include a larger proportion of younger children over the study period. Viral co-detections were identified in 25.5% of MP-positive cases, with the prevalence of co-detection being inversely correlated with age. Although the overall co-detection rate remained stable, MP-HAdV co-detections increased significantly in the second year (P < 0.001). Notably, the rate of co-detection was strongly correlated with the community circulation of other respiratory viruses (R = 0.85, P < 0.001), rather than the prevalence of MP itself.

Our data indicate that the post-pandemic epidemiology of MP in this coastal Chinese region was characterized by a shift from seasonal outbreaks to prolonged, high-level transmission, and notably, a broadening of the age distribution with expanded susceptibility among younger children. This downward shift deviates from the traditional concentration in school-aged populations and may reflect the evolving epidemiological dynamics of respiratory pathogens in the post-COVID-19 landscape. To the best of our knowledge, our findings offer regional insights that may help inform surveillance efforts and guide the development of age-targeted prevention strategies.

Not applicable.