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

Introduction: Microbial contamination of drinking water, particularly by pathogens such as 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 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 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 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 O157: H7. Using Microsoft ExcelTM and @RISKTM software, a Quantitative Microbial Risk Assessment model was constructed to quantify the risk of infection associated with 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 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.