Quantitative microbial risk assessment for Escherichia Coli O157: H7 via drinking water in the Gaza Strip, Palestine.

ABSTRACT

Introduction: Microbial contamination of drinking water, particularly by pathogens such as Escherichia coli O157 H7, is a significant public health concern worldwide, especially in regions with limited access to clean water like the Gaza Strip. However, few studies have quantified the disease burden associated with E. coli O157 H7 contamination in such challenging water management contexts. Objective: This study aimed to conduct a comprehensive Quantitative Microbial Risk Assessment to estimate the annual infection risk and disease burden attributed to E. coli O157 H7 in Gaza's drinking water. Methods: Applying the typical four steps of the Quantitative Microbial Risk Assessment technique-hazard identification, exposure assessment, dose-response analysis, and risk characterization-the study assessed the microbial risk associated with E. coli O157 H7 contamination in Gaza's drinking water supply. A total of 1317 water samples from various sources across Gaza were collected and analyzed for the presence of E. coli O157 H7. Using Microsoft ExcelTM and @RISKTM software, a Quantitative Microbial Risk Assessment model was constructed to quantify the risk of infection associated with E. coli O157 H7 contamination. Monte Carlo simulation techniques were employed to assess uncertainty surrounding input variables and generate probabilistic estimates of infection risk and disease burden. Results: Analysis of the water samples revealed the presence of E. coli O157 H7 in 6.9% of samples, with mean, standard deviation, and maximum values of 1.97, 9.74, and 112 MPN/100 ml, respectively. The risk model estimated a median infection risk of 3.21 × 10-01 per person per year and a median disease burden of 3.21 × 10-01 Disability-Adjusted Life Years per person per year, significantly exceeding acceptable thresholds set by the WHO. Conclusion: These findings emphasize the urgent need for proactive strategies to mitigate public health risks associated with waterborne pathogens in Gaza.