Emerging pathogens associated with acute respiratory infections in children before, during and after the COVID-19 pandemic in Hanoi, Vietnam

The COVID-19 pandemic has caused changes in respiratory infectious disease patterns. We analyzed de-identified data of microbiology assays of nasopharyngeal samples and blood samples of children with acute respiratory infection (ARI) visited Vinmec Times City International hospital in Hanoi, Vietnam from January 2019 to December 2023 to examine the overall pattern of viral and bacterial emerging pathogens associated with ARI in children before, during and after the COVID-19 pandemic. The data was aggregated by month and time series analysis and visualization was done. Bacterial Polymerase Chain Reaction (PCR) panel was done for 4125 samples, Mycoplasma pneumonia (MP) IgM was done for 5049 samples, bacterial culture was done for 10280 samples and viral PCR or rapid test was done for 42041 samples. After the COVID-19 pandemic, Haemophilus influenzae (HI) and Streptococcus pneumoniae (SP) have re-emerged as epidemic pathogens associated with lower respiratory tract infection (LRI). Influenza type A and type B have reestablished regular cycles of peaks in winter-spring months after an early rebound together with an unprecedented newly emergence of Human Adenovirus (HAdV) soon after the relief of COVID-19 restriction. Late after the COVID-19 pandemic, from middle of 2023, atypical pneumonia pathogen Mycoplasma pneumonia (MP) has emerged remarkably and becoming epidemic and there was also a small, brief emergence of Chlamydophila pneumoniae (CP) infection. Our data is useful to understand the influence of COVID-19 pandemic on the emergence or re-emergence of viral and bacterial respiratory infection pathogens in children and is useful for disease surveillance and public health intervention.