Impact of weather factors on Mycoplasma pneumoniae pneumonia.

BACKGROUND Although multiple combinations of weather factors may contribute to an increased incidence of Mycoplasma pneumoniae pneumonia, few studies have investigated the association between weather factors and cases of M pneumoniae pneumonia. METHODS Data on cases of M pneumoniae pneumonia and weather factors in Fukuoka, Japan from 1999 to 2007 were obtained and time-series analysis was used to assess the effects of weather variables on M pneumoniae pneumonia cases, adjusting for confounding factors. A total of 13 056 M pneumoniae pneumonia cases were reported during the 9-year study period, of which 12 234 (93.7%) were under 15 years of age. RESULTS The weekly number of M pneumoniae pneumonia cases increased by 16.9% (95% CI 11.3% to 22.8%) for every 1 degrees C increase in the average temperature and by 4.1% (95% CI 2.7% to 5.5%) for every 1% increase in relative humidity. CONCLUSIONS From 1999 to 2007, cases of M pneumoniae pneumonia increased significantly with increased average temperature and relative humidity in Fukuoka, Japan.