Spatiotemporal Dynamics of Scrub Typhus Transmission in Mainland China, 2006-2014.

Yi-Cheng Wu,Shen-Long Li,Wen-Biao Hu,Yong Wang,Yan-Song Sun,Zhi-Hai Han,Ricardo J Soares Magalhaes,Thomas A Weppelmann,Hai-Long Sun,Quan Qian,Ubydul Haque,Archie C A Clements,Wen-Yi Zhang,Yun-Xi Liu,Xin-Lou Li

doi:10.1371/journal.pntd.0004875

Abstract

BackgroundScrub typhus is endemic in the Asia-Pacific region including China, and the number of reported cases has increased dramatically in the past decade. However, the spatial-temporal dynamics and the potential risk factors in transmission of scrub typhus in mainland China have yet to be characterized.ObjectiveThis study aims to explore the spatiotemporal dynamics of reported scrub typhus cases in mainland China between January 2006 and December 2014, to detect the location of high risk spatiotemporal clusters of scrub typhus cases, and identify the potential risk factors affecting the re-emergence of the disease.MethodMonthly cases of scrub typhus reported at the county level between 2006 and 2014 were obtained from the Chinese Center for Diseases Control and Prevention. Time-series analyses, spatiotemporal cluster analyses, and spatial scan statistics were used to explore the characteristics of the scrub typhus incidence. To explore the association between scrub typhus incidence and environmental variables panel Poisson regression analysis was conducted.ResultsDuring the time period between 2006 and 2014 a total of 54,558 scrub typhus cases were reported in mainland China, which grew exponentially. The majority of cases were reported each year between July and November, with peak incidence during October every year. The spatiotemporal dynamics of scrub typhus varied over the study period with high-risk clusters identified in southwest, southern, and middle-eastern part of China. Scrub typhus incidence was positively correlated with the percentage of shrub and meteorological variables including temperature and precipitation.ConclusionsThe results of this study demonstrate areas in China that could be targeted with public health interventions to mitigate the growing threat of scrub typhus in the country.

Highlights

Scrub typhus, known as tsutsugamushi disease, is endemic in the so-called “tsutsugamushi triangle” area that includes Pakistan and Afghanistan in the west, far-eastern Russia and Japan in the north, and northern Australia in the south [1]
This study aims to explore the spatiotemporal dynamics of reported scrub typhus cases in mainland China between January 2006 and December 2014, to detect the location of high risk spatiotemporal clusters of scrub typhus cases, and identify the potential risk factors affecting the re-emergence of the disease
The results of this study demonstrate areas in China that could be targeted with public health interventions to mitigate the growing threat of scrub typhus in the country

Summary

Introduction

Known as tsutsugamushi disease, is endemic in the so-called “tsutsugamushi triangle” area that includes Pakistan and Afghanistan in the west, far-eastern Russia and Japan in the north, and northern Australia in the south [1]. There has been a drastic increase in both the frequency and geographic distribution of scrub typhus cases, which could signal the re-emergence of this neglected tropical disease [8,9,10,11]. The first reported case of a human infected with scrub typhus in China was identified in the southern province of Guangdong in 1948 [12]. Until the 1980s, scrub typhus cases primarily occurred in the regions south of Yangtze River with established natural foci including Zhejiang in the east and Yunnan in the west part of China [13, 14]. Scrub typhus is endemic in the Asia-Pacific region including China, and the number of reported cases has increased dramatically in the past decade. The spatial-temporal dynamics and the potential risk factors in transmission of scrub typhus in mainland China have yet to be characterized

Methods

Results

Conclusion