Kelly Moon

Despite sustained efforts over several decades, no region is projected to achieve universal sanitation access by 2030, according to international monitoring frameworks. Climate change is increasingly disrupting human and ecological systems, in turn deepening existing inequalities in access to essential services, including sanitation. Coupled with broader socio-economic and political dynamics, these pressures are expected to further widen the global sanitation service gap. Strengthening the resilience of sanitation systems to climate-related impacts represents a critical component of addressing this challenge. Building resilience requires an understanding of the attributes of sanitation systems and the adaptation actions across scales that contribute to their capacity to anticipate, withstand and recover from climate hazards. While existing scholarship has primarily examined the impacts of climate hazards on sanitation system performance, less attention has been given to resilience-building processes and practices. This systematic review is the first to synthesise the evidence on resilience in sanitation systems. The review identifies twenty-seven (n = 27) attributes and adaptation actions with potential to enhance resilience, none of which are currently considered in existing global monitoring processes. Only seventeen (n = 17) studies met the inclusion criteria, and empirical evidence remains scarce, highlighting substantial knowledge gaps. Findings also reveal a dominance of user-level, infrastructure focussed actions in low-income settings, with minimal evidence on operational or enabling environment strategies implemented by service providers or government actors. These findings highlight a substantial gap between identifying potential resilience-building measures and demonstrating how they contribute to resilience sanitation systems. Strengthening the evidence base requires greater emphasis on evaluating resilience outcomes, understanding interactions across the sanitation system, and examining how institutional and operational conditions shape adaptation over time. The findings provide a foundation for developing measurable indicators of climate resilience while highlighting the need for further empirical evidence to inform international monitoring frameworks and guide effective climate resilient sanitation planning.

Background Environmentally persistent zoonoses (EPZs), such as leptospirosis and melioidosis, are caused by pathogens that can survive outside of a host for over 48 hours. Their transmission is sensitive to climate hazards such as flooding, which can disperse pathogens and increase opportunities for spillover. Risk of exposure to EPZs during flooding is influenced by the vulnerability of exposed populations, which is shaped by social, economic, infrastructural, and environmental conditions. Understanding vulnerability to EPZs is therefore important for identifying populations most at risk during flooding and informing targeted disease control and equitable climate adaptation. We aimed to map how vulnerability is defined and measured in studies of flood-sensitive EPZs, characterise the vulnerability and flooding-related hazard indicators used, and assess how vulnerability and hazard were studied together. Methods This scoping review followed PRISMA-ScR guidance. Eleven bibliographic databases were searched (May 2025, updated January 2026) for epidemiological studies quantifying associations between vulnerability or hazard indicators and human health outcomes for eight EPZs. Data on study characteristics, definitions of vulnerability, vulnerability and hazard indicators, and methods used to study vulnerability and hazard together were extracted and synthesised. Results Seventy-eight studies were included. Only 16 explicitly used the terms "vulnerability" or "vulnerable," with heterogeneous usage. Vulnerability indicators (n=444) clustered into six domains but were dominated by sociodemographic characteristics (n=215), particularly sex/gender and age, while housing, environmental, infrastructural and health-service domains were less frequently represented. Hazard indicators (n=138) were dominated by broad meteorological (n=52) and seasonal (n=38) proxies. Most studies were cross-sectional, ecological or case-control, with relatively few time-series or cohort studies. Evidence was heavily concentrated on leptospirosis (41/78 studies). Vulnerability and hazard were generally treated as separate determinants of risk, with limited conceptual or analytical integration; only four studies formally tested interactions between them. Conclusion Vulnerability in EPZ research is inconsistently conceptualised and narrowly measured, with limited consideration of the environmental, infrastructural and service-level conditions that are particularly important for diseases transmitted at the human–animal–environment interface. Overall, the literature remains largely focused on identifying separate environmental and population risk factors rather than explaining how flooding produces unequal risks across populations. Flooding-related hazards are often characterised using broad proxies, while study designs and limited consideration of vulnerability and hazard together constrain understanding of who is most at-risk during flooding and why. Future research should use clearer vulnerability frameworks, measure relevant domains more comprehensively, improve characterisation of flooding-related hazards, and use interdisciplinary study designs capable of examining vulnerability and hazard together. This will strengthen evidence for targeted disease control and equitable climate adaptation.

Despite sustained efforts over several decades, no region is projected to achieve universal sanitation access by 2030, according to international monitoring frameworks. Climate change is increasingly disrupting human and ecological systems, in turn deepening existing inequalities in access to essential services, including sanitation. Coupled with broader socio-economic and political dynamics, these pressures are expected to further widen the global sanitation service gap. Strengthening the resilience of sanitation systems to climate-related impacts represents a critical component of addressing this challenge. Building resilience requires an understanding of the attributes of sanitation systems and the adaptation actions across scales that contribute to their capacity to anticipate, withstand and recover from climate hazards. While existing scholarship has primarily examined the impacts of climate hazards on sanitation system performance, less attention has been given to resilience-building processes and practices. This systematic review is the first to synthesise the evidence on resilience in sanitation systems. It identifies twenty-seven (n=27) attributes and adaptation actions with potential to enhance resilience. However, with only seventeen (n=17) studies meeting the inclusion criteria and limited empirical evidence, substantial knowledge gaps remain. These findings underscore the urgent need for targeted research and the development of measurable indicators of climate resilience to inform international monitoring frameworks and guide effective adaptation strategies.