ROLE OF HYDRO-CLIMATIC FACTORS AND SOCIOECONOMIC DETERMINANTS INFLUENCING MAJOR WATERBORNE DISEASE INCIDENCES IN VIRGINIA, USA

Abstract

ABSTRACT Climate change represents one of the most significant public health challenges of the 21st century, influencing infectious disease risks through changes in temperatures, precipitation, and drought patterns. Waterborne diseases are especially sensitive to these changes as climatic variability can alter the survival, transport, and exposure pathways of pathogenic microbes in water systems. This ecological case study examined the potential association of hydro-climatic and socioeconomic factors with coliform prevalence and waterborne disease incidence across eight Virginia counties using data spanning 2011 through 2020. Specifically, the study assessed (a) how air temperature, precipitation, drought severity, income, and education associated with coliform prevalence; (b) how these hydro-climatic and socioeconomic factors predict incidences of campylobacteriosis, giardiasis, and cryptosporidiosis; and (c) whether coliform prevalence serves as a proxy indicator of waterborne disease risk. Normality testing revealed a right skewed, zero-inflated distribution of the outcome variables. Bivariate analyses were first conducted for each predictor-outcome pair, followed by multivariable modeling using all hydro-climatic and socioeconomic variables. Zero-Inflated Gaussian Mixed Models (ZIGMMs) with random intercepts for each county were used to evaluate relationships among hydro-climatic and socioeconomic factors, coliform prevalence, and waterborne disease incidences. Coliform prevalence was found to be significantly associated with air temperature (p<.001), drought severity (p=.014), and calendar year (p<.001), which indicated that warmer and wetter conditions increased water contamination risk, while the overall decline in coliform prevalence reflected improvements in water infrastructure and quality oversight. Campylobacteriosis incidence increased significantly (p<.001) over the study period and was predicted by coliform prevalence (p=.043), and drought severity (p=.076). Giardiasis incidence was also predicted by coliform prevalence (p=.034) and marginally by drought severity (p=.064). In contrast, cryptosporidiosis incidence was associated primarily with calendar year (p=.041) and marginally with air temperature (p=.056) and education (p=.067), while showing no significant association with coliform prevalence. These findings indicate that hydro-climatic factors, particularly air temperature and drought severity, play a key role in shaping microbial contamination in water systems and enteric waterborne disease risks in Virginia. While pathogen-specific, routine coliform surveillance did serve as a valuable indicator of environmental conditions associated with waterborne disease risks. The steady decline in coliform prevalence observed across the study period highlights the effectiveness of statewide water quality interventions such as the Revised Total Coliform Rule (RTCR) and the Chesapeake Bay Total Maximum Daily Load (TMDL). Overall, these findings support the need for climate-informed water quality management, continuous coliform surveillance, and equity-focused interventions for vulnerable communities as climate risks intensify.