First report on prevalence and risk factors of severe atypical pneumonia in Vietnamese children aged 1-15 years

Background: Atypical pathogens such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila are increasingly recognized as important causes of community acquired pneumonia (CAP) worldwide. Such etiological data for Vietnam is scarce and clinical doctors lack accurate information on which to base their diagnosis and treatment of pneumonia. This study identifies the prevalence and risk factors of severe community acquired pneumonia due to these atypical pathogens (severe-ApCAP) in children aged 1-15 years with CAP in a pediatric hospital in Hanoi, Vietnam. Methods: 722 hospitalized children with CAP were recruited for detecting those atypical pathogens, using multiplex PCR and ELISA. Clinical and epidemiological data were collected. Multivariate logistic-regression analyses were performed to evaluate the associations of potential risk factors with severe-ApCAP. Results: Among 215 atypical pathogen-positive CAP cases, 45.12% (97215) were severe-ApCAP. Among the severe-ApCAP group, 55.67% (5497) cases were caused by pure atypical pathogens and 44.33% (4397) resulted from a co-infection with typical respiratory pathogens. M. pneumoniae was the most common, with 86.6% cases (8497) in the severe-ApCAP group, whereas C. pneumoniae and L. pneumophila were less frequent (6.19% and 7.22%, respectively). The highest rate of severe-ApCAP was in children younger than two years (65.98%). The differences related to age are statistically significant (P = 0.008). The factors significantly associated with severe-ApCAP were age (OR = 0.84, 95% CI = 0.75-0.93, P = 0.001), co-infection with typical bacteria (OR = 4.86, 95% CI = 2.17-10.9, P < 0.0001), co-infection with respiratory viruses (OR = 4.36, 95% CI = 1.46-13.0, P = 0.008), respiratorycardiac system malformation (OR = 14.8, 95% CI = 1.12-196, P = 0.041) and neonatal pneumonia (OR = 11.1, 95% CI = 1.06-116, P = 0.044). Conclusions: Severe-ApCAP presented at a significant rate in Vietnamese children. More than 50% of severe-ApCAP cases were associated with pure atypical pathogen infection. M. pneumoniae appeared most frequently. The highest rate of severe-ApCAP was in children younger than two years. Younger age and co-infection with typical bacteria or viruses were the most significant risk factors, while respiratorycardiac system malformation and neonatal pneumonia were additional potential risk factors, associated with severe-ApCAP in Vietnamese children.