Emerging pathogens associated with acute respiratory infections in children in Hanoi, Vietnam: an analysis of microbiology assay data from 2019 to 2023

<ns3:p> Background The COVID-19 pandemic has caused changes in respiratory infectious diseases. Examining the patterns of pathogens associated with acute respiratory infection (ARI) in children before, during, and after the COVID-19 pandemic would help to understand the impact of the pandemic on pathogen emergence or re-emergence. Methods We analyzed de-identified data from microbiology assays of nasopharyngeal and blood samples of children ≤15 years old with ARI who visited Vinmec Times City International Hospital in Hanoi, Vietnam from 01/01/2019 to 31/12/2023. The data were aggregated by month, and time-series analysis and visualization were performed. Results A Bacterial Polymerase Chain Reaction (PCR) panel was performed on 4,125 samples (67% positive), <ns3:italic>Mycoplasma pneumonia</ns3:italic> (MP) IgM was performed on 5,049 samples (39% positive), bacterial culture was performed on 10,280 samples (43% positive), and viral PCR or rapid test was performed on 42,300 samples (23% positive). After the COVID-19 pandemic from mid-2022, <ns3:italic>Haemophilus influenzae</ns3:italic> (HI) and <ns3:italic>Streptococcus pneumoniae</ns3:italic> (SP) have re-emerged as epidemic pathogens associated with lower respiratory tract infection (LRI). <ns3:italic>Influenza type A</ns3:italic> and <ns3:italic>type B</ns3:italic> have re-established regular cycles of peaks in winter-spring months after an early rebound together with an unprecedented new emergence of <ns3:italic>Human Adenovirus</ns3:italic> (HAdV) soon after the relief of COVID-19 restriction in mid-2022. Late after the COVID-19 pandemic, from mid-2023, atypical pneumonia pathogen <ns3:italic>Mycoplasma pneumonia</ns3:italic> (MP) has emerged remarkably and has become epidemic; there was also a small, brief emergence of <ns3:italic>Chlamydophila pneumoniae</ns3:italic> (CP) infection. Conclusion Our data characterize the influence of the COVID-19 pandemic on the patterns of respiratory infection pathogens in children and is useful for disease surveillance and public health interventions. </ns3:p>