Epidemiology of Legionella and Climatic Variables in Seoul, Korea

ABSTRACT

Legionella species are abundant in the built environment and are increasingly recognized as a cause of Legionnaires' disease (LD). As the number of cases of Legionnaires' disease acquired by local communities in the Seoul metropolitan area in Korea has been increased, there was concern that changes in environmental factors could affect disease outbreaks. We described the association between climatic variables and occurrence of legionellosis in Korea and Legionella detection rate in Seoul area. A total of 418 cases of legionellosis were reported between 2014 and 2017. There was a seasonal peak in summer. LD continuously occurred from early spring to winter every year and rapidly increased in summer. In the regression analysis, the primary variables of interest- PM2.5 (µg/m³), NO₂ (ppb), and a number of the date of issue O₃ warning were not significant except for average temperature (R²=0.8075). The Legionella detection rate in Seoul, Korea showed a trend similar to precipitation (P=0.708, ANOVA). A relatively high proportion of Legionella detection rate was shown, especially cooling tower (17.7%) and public bath (19.3%). This finding is in line with current understanding of the ecological profile of this pathogen and supports the assertion that legionellosis occurs through contamination of water sources.