Spatio-temporal patterns of scrub typhus in mainland China, 2006-2017

Background: Scrub typhus, a serious public health problem in the Asia-Pacific area, is endemic in the “tsutsugamushi triangle” area. Scrub typhus has been widespread and has become a significant health concern in China. However, spatiotemporal patterns need to be investigated further. Objective: This study aims to explore spatiotemporal patterns, diffusion characteristics and regional distribution differences of scrub typhus cases in mainland China from January 2006 to December 2017. Method: Monthly cases of scrub typhus reported at the county level during 2006–2017 were obtained. Time-series analyses, spatial distribution analyses, spatial diffusion analyses, spatial autocorrelation analyses and space-time scan statistic analyses were used to explore spatiotemporal characteristics of scrub typhus. Results: A total of 121 251 scrub typhus cases were reported in 30 provinces (or municipalities) of mainland China during 2006–2017, which rose exponentially. There were seasonal characteristics from June to November for scrub typhus. Scrub typhus had been diffused from south, southwest, southeast and eastern coasts to center, north, northeast and northwest in mainland China. Scrub typhus occurrences were from point to surrounding regions, and from south to north every year. The peak periods of scrub typhus became longer and longer from north to southwest to south in mainland China. There existed a single peak in Southwest region and North region, respectively, but existed a bimodal peak for South region. Scrub typhus cases were clustered in Yunnan, Guangdong, Guangxi, Fujian and Anhui among June to November. The scrub typhus epidemics in Guangdong and Yunnan were the most serious. Conclusions: The results in this study can be guide targeted public health interventions against scrub typhus at the county level. Author summary: Scrub typhus is a bacterial zoonosis caused by Orientia tsutsugamushi and is popular in the Asia-Pacific area. Nowadays scrub typhus has been widespread and causes a considerable burden on public health and economy in China. We investigated spatiotemporal patterns, diffusion characteristics and regional distribution differences of scrub typhus cases in mainland China from 2006 to 2017. The majority of scrub typhus cases were reported in June to November, and 98.3% of the total scrub typhus cases during 2006–2017 were reported in South region, Southwest region and North region. Scrub typhus had been diffused in mainland China except Qinghai. Scrub typhus occurrences were from point to surrounding regions, and from south to north every year. The peak periods of scrub typhus turn longer, and there existed a single peak to a bimodal peak from north to south. Scrub typhus cases were clustered in Yunnan, Guangdong, Guangxi, Fujian and Anhui during June to November. The scrub typhus epidemics in Guangdong and Yunnan were the most serious.