Effects of meteorological factors on scrub typhus in a temperate region of China

Abstract

Scrub typhus is emerging and re-emerging in many areas: climate change may affect its spread. To explore the effects of meteorological factors on scrub typhus, monthly cases of scrub typhus from January 2006 to December 2012 in the Laiwu district of temperate northern China were analysed. We examined the correlations between scrub typhus and meteorological factors (and their delayed effects). We built a time-series adjusted negative binomial model to reflect the relationships between climate variables and scrub typhus cases. The key determinants of scrub typhus transmission were temperature, relative humidity and precipitation. Each 1°C increase in monthly average temperature in the previous 3 months, each 1% increase in monthly relative humidity in the previous 2 months and each 1 mm increase in monthly precipitation in the previous 3 months induced 15·4%, 12·6% and 0·7% increases in the monthly number of cases, respectively. In conclusion, scrub typhus is affected by climate change in temperate regions.

Fig. 1.

Scrub typhus cases in Laiwu, China from 2006 to 2012.

Fig. 2.

Monthly means of climatic factors in Laiwu, China during 2005–2012.

Fig. 3.

(a) The autocorrelation function and (b) partial autocorrelation function of the number of cases in Laiwu, China. , Coefficient. The horizontal lines indicate the upper and lower confidence limits.

Fig. 4.

Notified cases, model fit cases from 2006 to 2011, and predictive cases of scrub typhus in 2012 according to the time-series adjusted negative binomial model.