Spatiotemporal and demographic characteristics of scrub typhus in Southwest China, 2006–2017: An analysis of population‐based surveillance data

Abstract

Scrub typhus is a life-threatening vector-borne disease. During the past decade, the number of areas affected by this disease has expanded in many countries. In this study, we aim to identify the spatiotemporal and demographic characteristics of scrub typhus in Southwest China, an emerging endemic region for scrub typhus. Population-based surveillance data capturing scrub typhus cases in two provinces of Southwest China during 2006-2017 were retrieved. Descriptive temporal and spatial analyses were conducted and stratified by age group. The space-time scan statistic was used to identify spatiotemporal clusters of scrub typhus occurrence at the county level. During the study period, 30,001 scrub typhus cases were recorded in Southwest China, with a total of 61.0% (191/313) of counties being affected; most cases (94.3%) occurred in rural areas. The annual incidence rate increased substantially from 0.25/100,000 in 2006 to 5.38/100,000 in 2017 (>21-fold change). The 0to 4-year-old and 45-to 64-year-old subgroups had the highest cumulative incidence rates (57.46 and 32.98/100,000, respectively). Furthermore, since 2006, the 0-to 4-year-old (slope = 0.83, p < .01) and 45-64-year-old (slope = 0.69, p < .01) age groups have had the highest increases in incidence of all age groups. The most likely spatial cluster of overall cases (relative risk = 4.13, p < .01) occurred in the southern region of Southwest China and included 41 high-risk counties. In conclusion, scrub typhus appears to be widely distributed and rapidly increasing in Southwest China. Young

Etiology of acute febrile illnesses in Southern China: Findings from a two-year sentinel surveillance project, 2017–2019

“…Scrub typhus is a nationally notifiable disease in China. A previous analysis of 93,481 scrub typhus cases reported between 2006 and PLOS ONE 2016 identified high-risk locations in rural and recently developed areas in Yunnan and Guangdong Provinces [34], with human infections typically peaking in summer and autumn each year [33]. Patients with positive TAC results for O. tsutsugamushi in our project followed this seasonal pattern (consistent with the lifecycle of the mite, Leptotrombidium delicense, responsible for human infections in southern China).…”

Epidemiological characteristics and spatiotemporal patterns of scrub typhus in Fujian province during 2012–2020

“…growth of the rodent and chigger mite populations was produced increasing the possibility of human exposure and the formation of new natural foci for scrub typhus in previously unaffected areas [13]. For example, the construction of the first national ecological civilization pilot zone was approved in 2016 leading to the incidence rising until its highest point in 2018.…”

“…Seasonal decomposition analysis indicated that local acquired scrub typhus cases were highest in summer (June-July), followed by autumn (September-October). We believed that the seasonal pattern was influenced by the vector cycles and Leptotrombidium deliense is the major mite species and main vector is in the south of the Yangtze River in China [13,37,38]. The key determinants of scrub typhus transmission were temperature, relative humidity and precipitation and therefore, climatic conditions during June-October and abundant food in the harvest season might be most appropriate to the rodent host of Leptotrombidium delicense [38][39][40][41].…”

“…Spatiotemporal analysis techniques have been widely employed to investigate infectious diseases [12][13][14][15]. On the other hand, knowledge of the spatial-temporal patterns of scrub typhus in Fujian province is essential to minimize the public health burden imposed by the severe infection because the potential disease risks in the area is currently underestimated and studies remain poorly conducted.…”

Analysis on infestation and related ecology of chigger mites on large Chinese voles (Eothenomys miletus) in five provincial regions of Southwest China

“…Scrub typhus is an acute febrile zoonosis (zoonotic disease), which is prevalent in some parts of Asian (including China) and pacific regions with about one million new cases each year and more than one billion people at risk ( Chakraborty and Sarma 2017 ). From 2006 to 2017, the annual incidence of scrub typhus increased more than 21 times in Southwest China ( Xin et al, 2020 ). Besides transmitting O. tsutsugamushi , some chiggers are also suspected to be the potential vector of hantavirus, the pathogen of hemorrhagic fever with renal syndrome (HRFS) ( Yu and Tesh 2014 ; Ding et al, 2021 ; Xiang et al, 2021 ).…”