Patterns of Bacillary Dysentery in China, 2005-2010

Abstract

Although the incidence of bacillary dysentery in China has been declining progressively, a considerable disease burden still exists. Few studies have analyzed bacillary dysentery across China and knowledge gaps still exist in the aspects of geographic distribution and ecological drivers, seasonality and its association with meteorological factors, urban-rural disparity, prevalence and distribution of Shigella species. Here, we performed nationwide analyses to fill the above gaps. Geographically, we found that incidence increased along an east-west gradient which was inversely related to the economic conditions of China. Two large endemically high-risk regions in western China and their ecological drivers were identified for the first time. We characterized seasonality of bacillary dysentery incidence and assessed its association with meteorological factors, and saw that it exhibits north-south differences in peak duration, relative amplitude and key meteorological factors. Urban and rural incidences among China's cities were compared, and disparity associated with urbanization level was invariant in most cities. Balanced decrease of urban and rural incidence was observed for all provinces except Hunan. S. flexneri and S. sonnei were identified as major causative species. Increasing prevalence of S. sonnei and geographic distribution of Shigella species were associated with economic status. Findings and inferences from this study draw broader pictures of bacillary dysentery in mainland China and could provide useful information for better interventions and public health planning.

Keywords: Shigella species; bacillary dysentery; ecological drivers; geographic and temporal patterns; high-risk regions; meteorological factors; seasonality; urban and rural disparities.

Figure 1

Annual average and change of bacillary dysentery incidence in each province in China, 2005–2010. Annual incidence for each year is shown in Figure S3. The map was created using the ArcGIS 10.0 software (ESRI Inc.).

Figure 2

Seasonality of bacillary dysentery incidence and meteorological factors in each province: (a) peak duration, number of months with a higher incidence than half of peak incidence; (b) relative amplitude, ratio of peak and bottom incidence; (c) peak month; (d) association between relative humidity and incidence; (e) key meteorological indicator; (f) climate types in China [34]. The maps were created using the ArcGIS 10.0 software (ESRI Inc.).

Figure 3

Endemically high-risk regions in southwest and northwest China and relevant environmental factors. Map was drawn at county-level and the color blocks represented annual average incidence of bacillary dysentery during 2005–2010. The two high risk regions in western China are marked in blue. Gray line: boundary of municipality cities, prefecture-level cities, autonomous prefectures, prefectures and leagues. The maps were created using the ArcGIS 10.0 software (ESRI Inc.).

Figure 4

Percent change of bacillary dysentery incidence in urban and rural areas by province. Exact incidence and change of incidence in urban and rural area of each province during 2005–2010 is shown in Figure S6.

Figure 5

Average prevalence of S. sonnei in China, 2005–2010. Small color blocks are drawn according to study areas of the included studies. Background color in each province is selected according to estimation of the prevalence of S. sonnei. Places that are not dominated by S. sonnei are dominated by S. flexneri. The maps were created using the ArcGIS 10.0 software (ESRI Inc.).