Patterns of acute watery diarrhea in Fiji: understanding the implications for water and sanitation services

BACKGROUND: Diarrheal disease, including acute watery diarrhea (AWD), remains a persistent global health challenge, particularly in settings with inadequate water and sanitation infrastructure. Understanding the local epidemiological features of AWD is a crucial first step to inform effective public health intervention. This study examines the AWD trends in Fiji and their association with water and sanitation service levels as defined by the WHO/UNICEF Joint Monitoring Programme. METHODS: This ecological study analysed longitudinal syndromic surveillance data on AWD cases reported in Fiji's Central and Western Divisions from April 2016 to December 2021, alongside census derived water and sanitation data. Age-specific trends, seasonal patterns, and district-level variations were assessed using descriptive statistics and Pearson's correlation analyses. The associations between AWD incidence, water and sanitation service levels were evaluated using negative binomial regression, adjusting for district-level population confounders. Additionally, population attributable risk (PAR) was calculated to estimate the proportion of AWD cases linked to unimproved water and sanitation services. RESULTS: Children under 5 years old (U5) had the highest incidence of AWD throughout the study period, with both age groups showing a seasonal trend from February to April annually. AWD rates declined during the period when COVID-19 travel restrictions were in place. A strong correlation existed between U5 and O5 cases across all years (R = 0.59-0.88; 95% CI: 0.45-0.92; p < 0.001). Nearly 18% of AWD cases were attributable to unimproved water (PAR 17.46%) and sanitation (PAR 17.80%). Access to safely managed water service reduced AWD risk (reference category), while unimproved water (RR 3.42; 95% CI: 2.66-4.38) and sanitation (RR 7.56; 95% CI: 4.21-13.58) service levels posed the highest risks. CONCLUSION: Advancing access to safely managed water and sanitation is essential to mitigate AWD. Investments in water and sanitation infrastructure particularly in underserved and high-risk areas should be prioritised. The findings underscore the importance of context-specific Water and Sanitation interventions in Pacific Island settings.