Facilitators and barriers to safely managed water and sanitation: A spatio-temporal investigation of the association between socioeconomic factors and shigellosis incidence

Abstract

The lack of access to safe drinking water and sanitation worldwide has contributed to the occurrence of shigellosis, a waterborne infectious disease. Previous research has shown that shigellosis can be prevented by access to safe drinking water and adequate sanitation, however access is facilitated or hindered by socioeconomic conditions. The effects of socioeconomic conditions on shigellosis incidence are unclear in the context of rural China. This thesis explored the spatial patterns of shigellosis over time and the spatio-temporal association between shigellosis incidence and socioeconomic conditions of the rural population in Jiangsu province.

Choropleth maps were created to understand the geographic distribution of shigellosis incidence at the county level. Spatial analysis methods such as spatial autocorrelation, Local Moran’s I, and the Getis Ord Gi were used to identify disease clusters, outliers, and hotspots. Based on the findings from the hot spot analysis and evidence from literature, a field visit to the northwestern county of Suining was conducted to further investigate the relationships between water and sanitation access and shigellosis incidence in the rural context. The temporal variability of the association between socioeconomic factors and shigellosis at the county level was investigated using negative binomial and quasi-Poisson regression models. The spatial relationship between socioeconomic factors and shigellosis at the county level was explored using a Bayesian spatial model.

Results showed that shigellosis morbidity was characterized by significant declines in most regions from 2011 to 2015; however, high morbidity rates were still evident in the northwestern region of Jiangsu. At the county level, the factors such as the number of hospital beds per capita and the percentage of rural households has shown to be significantly associated with shigellosis incidence for years 2011, 2012, and 2014, respectively. The percentage of rural households was negatively correlated with shigellosis incidence; this relationship was further confirmed by results from the Bayesian spatial model. In addition, results showed that rural employment and the number of hospital beds per capita, respectively, were correlated with a decrease in shigellosis incidence. In contrast, the number of hospitals per capita was positively correlated with an increase in shigellosis incidence. Underreporting of shigellosis in rural areas was suspected to be the cause of the low rate of shigellosis in rural areas. The quality of the rural healthcare system and living conditions may have influenced this underreporting. Thus, a more active surveillance method should be adopted to gauge the real occurrence of shigellosis amongst the rural population.