Annual and seasonal patterns in etiologies of pediatric community-acquired pneumonia due to respiratory viruses and Mycoplasma pneumoniae requiring hospitalization in Korea

Background: Community–acquired pneumonia (CAP) is one of the leading worldwide causes of childhood morbidity and mortality and its disease burden is affected by age and etiologies with time-dependent changes. We aimed to investigate the annual and seasonal patterns in etiologies of pediatric CAP requiring hospitalization. Methods: We conducted a retrospective study in 30,994 children (0-18 years old) with CAP between 2010 and 2015 at 23 nationwide hospitals in Korea. Mycoplasma pneumoniae (MP) pneumonia was clinically classified into macrolide-sensitive MP, macrolide-less effective MP (MLEP) and macrolide-refractory MP (MRMP) based on fever duration after initiation of macrolide treatment, regardless of the results of in vitro macrolide sensitivity tests. Results: MP and respiratory syncytial virus (RSV) were the two most commonly identified pathogens of CAP. With the two epidemics of MP pneumonia (2011 and 2015), the rates of clinical MLEP and MRMP pneumonia showed increasing trends of 36.36% of the total MP pneumonia. In children less than 2 years of age, RSV (34.01%) was the most common cause of CAP, followed by MP (9.44%), whereas MP was the most common cause of CAP in children 2-18 years of age. Systemic corticosteroid was most commonly administered in MP pneumonia. The rate of hospitalization in intensive care unit was highest for RSV pneumonia, and ventilator care was most commonly needed in cases of adenovirus pneumonia. Conclusions: The present study provides fundamental data for establishment of public health policies to decrease disease burden due to CAP as well as for improvement of pediatric health.