Mycoplasma Pneumoniae: A Cross-sectional Population-based Comparison of Disease Severity in Preschool and School-age Children

Background: Mycoplasma pneumoniae causes epidemics of upper respiratory disease and pneumonia. It is thought that M. pneumoniae usually causes milder upper respiratory disease in preschool children, with a greater chance of pneumonia in school-age children. In this population-based cross-sectional study, we present evidence that severe M. pneumoniae infection is more common in preschool children than previously thought. Methods: During an M. pneumoniae epidemic in our area, widespread health service and public awareness lead to extensive testing for M. pneumoniae . Medical records of hospital-referred M. pneumoniae –positive children were assessed retrospectively for respiratory disease and chest radiographic results. Severe disease was defined as supplementary oxygen or fluid requirement, mechanical ventilatory support or neurologic disease. Age-specific population figures were used to calculate incidence during the study period. Those who were 0–5-year-olds were considered preschool, whereas 6–17-year-olds were considered school-aged. Results: Thirty-seven preschool and 55 school-age children were referred to the hospital and tested positive for M. pneumoniae . Twenty-two (60%) preschool and 23 (42%) school-age children had severe disease [incidence 56 vs. 29 per 100,000; relative risk: 1.9; 95% confidence interval (CI): 1.06–3.4; P = 0.03]. Twenty (54%) preschool and 19 (35%) school-age children had severe pneumonia (incidence 51 vs. 24 per 100,000; relative risk: 2.1; 95% CI: 1.1–3.9; P = 0.03). Conclusions: During an M. pneumoniae epidemic in Akershus and North Oslo in 2011–2012, preschool children infected with M. pneumoniae had significantly higher risk of severe disease, particularly severe pneumonia, when compared with school-age children. M. pneumoniae should be considered a potential pathogen in younger children with respiratory distress, particularly during an epidemic period.