Climate factors associated with incidence of acute respiratory infectious disease in Korea

INTRODUCTION:  Spatio-temporal patterns of acute respiratory infectious diseases (ARI) often suggest that climate factors like temperature and humidity play an important role its seasonality. However, their effects on regional variation in the timing of annual epidemics have not been fully assessed yet. We explored the effect of relative humidity, solar radiation, temperature-humidity index and daily temperature-variation on ARI incidence in 3 geographical positions (Seoul, Ulsan, and Chungju) in Korea. 

METHODS:  We used the Korean National Health Insurance Review and Assessment Database to estimate the weekly incidence of ARI from 2006 to 2010. ARI was defined by ICD-10 codes of J00-J06. Air temperature, relative humidity, solar radiation and rain fall from 1st week 2006 to 52nd week 2010 observed by Korean Meteorological Administration were used in this analysis. Descriptive statistics of ARI by region and seasons were generated. Correlation analysis between the climate factors and ARI was done with scatter graphs.  The incidence of ARI and climate factors were also analyzed using time-series analysis based on transfer function model to explore the effect of climate factors.

RESULTS:  Mean weekly ARI incidence per 1,000 populations during study periods was highest in Ulsan (34.0±9.9) than that of Seoul (18.1±8.2) or Chungju (28.7±8.2) with statistical significance.  Mean monthly incidence of ARI was highest in April in all area, and followed by November and December. The ARI incidence was highest when the daily lowest temperature was in 5℃-9℃. The higher daily temperature difference, the higher ARI incidence was observed. Air temperature, relative humidity, solar radiation, and rainfall were statistically significant factors in each region in correlation analysis, but the influential climate factors were different from region to region in time-series analysis.

CONCLUSIONS:  Climate factors including daily temperature difference and relative humidity are significant determinants of ARI, but the influence of the climate factor varies from region.