Diarrhea remains a major threat to public health around the world. According to the Global Burden of Disease , in 2016, diarrhea ranked as the eighth leading cause of death among all age groups and the fifth leading cause of death for children less than five years old. Residents mostly affected by diarrhea as a major threat to populational health, especially for children aged less than five years old were found to be mainly distributed in underdeveloped regions including Africa, South East Asia and the Eastern Mediterranean [2, 3]. Under-five children in developing countries suffered from an average of 2.9 diarrhea onsets each year , with approximately one-third of total onsets being moderate or severe cases. In China, more than a million diarrhea cases were reported in 2018 alone, with the morbidity of diarrhea found to be 92 cases per hundred thousand population, making it the second highest among notifiable diseases in terms of incidence .
Diarrhea, a gastrointestinal infection, can be caused by a wide range of pathogens, including bacteria, viruses, and parasites . A critical transmission route of diarrhea is the fecal-oral route, such as the consumption of fecally contaminated food, drinking water as well as via person-to-person contact due to poor hygiene [7–9]. The morbidity and distribution of diarrhea would be affected by various factors, including sociodemographic factors (age, education, income etc.) [10–12], environmental and sanitation factors (poor access to a good water source and poor sanitation) [13, 14], and climate factors (rainfall, temperature and humidity) [15–17].
Diverse efforts have been made in attempt to reduce the morbidity of diarrhea in a worldwide range, among which improved water, sanitation, and hygiene (WASH) facilities such as piped water, protected shallow wells, and non-shared toilets have been widely accepted as cost-effective ways for reducing the morbidity of diarrhea [18–20]. In China, the rapid socioeconomic development has significantly improved the nationwide penetration of improved water, sanitation, and hygiene facilities. For example, according to National Statistical Yearbook, in urban regions, the penetration of piped water increased from 63.9% in 2000 to 98.36% in 2018 . However, various factors have posed huge obstacles for Chinese residents in obtaining actual access to improved WASH . For example, in 2008, 2.81 million disability-adjusted life years (DALYs) and 62,800 deaths were attributed to unsafe water and poor sanitation or hygiene in China. Water pollution in the nation was found to be inadequately controlled  as 44% of nationwide rural water supplies failed to meet minimum drinking water quality standards . Under such circumstances, it is noteworthy that improved WASH facilities are not necessarily associated with improved hygiene behaviors such as safe feces disposal or improved handwashing procedures, which has been highlighted by researchers such as Lamichhane  while has received relatively inadequate investigation based on previous literature.
As improved hygiene behaviors should be addressed as an indispensable aspect in achieving improved public health outcomes in addition to the enhancement of WASH facilities, the optimization of health education programs as well as health service delivery at primary healthcare level should be emphasized as an essential strategy in improving residents’ actual access to improved WASH thus further reducing the incidence of diarrhea. Specifically, primary healthcare institutions have been playing critical roles in China as gatekeepers throughout the process of infectious disease prevention and control, including cutting off transmission routes, protecting vulnerable populations, providing treatment for infected patients as well as providing health educational programs and assisting in the maintenance of WASH facilities among communities. Under such context, it is not difficult to imagine that improved WASH maintenance and health education programs at primary healthcare level are very much likely to achieve the reduction of nationwide diarrhea morbidity via improving residents’ appropriate use of WASH facilities, minimizing the infection of well water in rural areas via disinfection procedures as well as monitoring the concentration of bacterial accumulation in water pipes on a regular surveillance basis.
Despite the significant contributions that primary healthcare institutions have been playing in the process of infectious diseases prevention and control, studies focused on investigating the roles of primary healthcare workers in reducing diarrhea morbidity remain limited based on previous literature. Specifically,a couple of studies [26–28] have verified the effectiveness of regular visits conducted by community healthcare workers (similar with primary healthcare workers) in reducing childhood diarrhea morbidity, while several other studies [29, 30] have highlighted the significant role of community healthcare workers in improving residents’ health literacy. However, evidences collected under the context of China’s healthcare system were found to be very limited in this aspect, while none of the currently existed studies have ever been focused on evaluating healthcare resource allocation as a determinant for healthcare institutions’ performances in reducing residents’ diarrhea morbidity, especially at primary healthcare level where the distribution of health resource is mainly reflected by the number of healthcare professionals.
In order to bridge such gap embedded in previous literature, this study has been designed for exploring the association between the number of primary healthcare workers and residents’ diarrhea morbidity in the community range in order to provide evidence-based suggestions for healthcare resource allocation at the community level. In addition, our findings were expected to provide practical implications for other infectious diseases as diarrhea has a list of characteristics typical of communicable diseases including high incidence, diverse pathogens and transmission routes, as well as would be affected by sociodemographic factors and the construction of health infrastructures at regional levels. Diarrhea morbidity and relevant data from 2017 to 2019 in Sichuan Province, China were collected for analysis. The spatial lag fixed effects panel data model was adopted to explore the relationship between the number of primary healthcare workers and diarrhea morbidity in the community range. The local indicators of spatial association (LISA, Local Moran’ I) analysis was used to determine areas where increased healthcare resources should be allocated.
This study was expected to contribute to the relevant literature in two aspects. First, our study was expected to bridge the gap embedded in similar studies through exploring the association between the number of primary healthcare workers and diarrhea morbidity at community levels. Through identifying the role of primary healthcare resource allocation in infectious diseases prevention and control in China, our findings were also expected to assist in the formulation of region-specific policies by providing evidences on specific locations of high incidence clusters. Second, our study was expected to add evidences to previously published studies in this field which were conducted at county levels via providing new evidences collected at community levels, which served as a better solution to heterogeneity issue as the spatial variation of disease morbidity would be detected and analyzed at a smaller health administrative unit.
This paper has been structured to contain the following sections. Specifically, an overview of health authorities as well as their roles in the process of infectious diseases prevention and control was briefly described in the Background section. The study area, data sources and empirical strategies were described in the Methods section, which was followed by Results and Discussion sections where findings and discussions were provided, respectively.