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

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.

Epidemiological dynamics of dengue fever in mainland China, 2014–2018

“…In order to perform spatio-temporal analysis, dengue cases were aggregated at the county level according to national codes of current addresses, and then were geocoded and matched to the county-level administrative boundaries using ArcGIS version 9.5 (ESRI, 2017). There are 31 provinces (or municipalities) comprised of 2 922 counties in mainland China, with populations ranging from 7,123 to 5,044,430, with geographic areas ranging from 5.4 to 197,346 square kilometers (Wu et al, 2016).…”

Spatiotemporal patterns and determinants of dengue at county level in China from 2005–2017

“…Specifically, Global Moran's I index ranges from À1 to 1, in which 0 represents a random spatial distribution, below 0 a scattered spatial distribution and above 0 clustering distribution. LISA estimated the local Moran's I between one certain county and surrounding counties, indicating the localized significant hotspots (High-High), coldspots (Low-Low), and outliers (High-Low and Low-High) (Sun et al, 2018;Wu et al, 2016).…”

Analysis on epidemiological characteristics of 4 species natural-focal diseases in Shandong Province, China in 2009-2017: a descriptive analysis

“…Their density fluctuations are closely related to the seasonal distribution of scrub typhus cases, and the monthly distribution of scrub typhus cases was consistent with the fluctuation of Leptotrombidium scutellare[9, 30, 31]. Third, some studies have shown that meteorological factors affect the incidence of scrub typhus, such as temperature, sunlight, precipitation, etc[16, 32, 33]. The climatic conditions of Shandong Province from September to November may be most suitable for the occurrence of scrub typhus.…”

“…Shandong Province as an emerging epidemic focus of scrub typhus, the number of reported cases in where has increased rapidly since the first cases reported in Shandong Province in 1986[16-19]. This study shows that the number of cities with scrub typhus cases is relatively stable and the number of annual reported cases of scrub typhus increased slowly before 2013, but the sharp increase from 2013 to 2014 and then has been maintained at a high level.…”