Environmental Drivers of Diarrheal Disease Risk in Ho Chi Minh City, Vietnam

Abstract

Background: Despite recent advances in hygiene and sanitation, diarrheal disease remains a lead in cause of mortality in children under five. Reducing the global burden of diarrheal disease necessitates further understanding of the drivers of diarrheal disease incidence. Poorly understood are the impacts of environmental factors on diarrheal disease transmission rates, with rainfall and flooding of particular interest given the role that water plays in spreading fecal contaminants. Methods: Using a unique dataset collected over six years in Ho Chi Minh City, Vietnam, spatiotemporal variability in all-cause diarrheal disease incidence was assessed. Rainfall, water level, humidity, and temperature were evaluated as possible drivers of diarrheal disease incidence. Elevation, socioeconomic status, imperviousness, and rain runoff were tested for their ability to mediate the effect of environmental factors on diarrheal disease incidence. Additionally, an epidemic model was developed to further explore the transmission dynamics of rotavirus, known to cause a high number of diarrhea hospitalizations in Ho Chi Minh City. Results: All of the environmental factors evaluated were significantly associated with diarrheal disease incidence during the study period, indicating that environmental fluctuations drive diarrheal disease incidence. Rainfall was negatively associated with diarrhea, whereas flooding was positively associated with diarrhea. Additionally, elevation was found to have a protective effect against diarrhea. Higher elevation districts experienced fewer diarrhea hospitalizations, suggesting that these districts were less susceptible to diarrheal disease transmission driven by flooding. The significance of these findings is tempered by the suggestion that environmental effects vary by enteropathogen. The results of the epidemic model indicate that rotavirus incidence is driven by intrinsic seasonality, rather than fluctuations in environmental factors.Conclusions: Targeting environmental drivers of diarrheal disease has the potential to serve as a meaningful strategy for reducing diarrheal disease incidence. For example, the protective effects of rainfall and elevation can be replicated through decontamination of aquatic reservoirs and flood-contral effots. At the same time, the widespread prevalence of rotavirus and other enteropathogens with limited susceptibility to environmental factors indicates the importance of vaccination as a control measure.