Vulnerability to flood-sensitive environmentally persistent zoonoses: a scoping review

Ellie A Delight , Kelly Moon , Wendy Sharpe , Joseph Wells, Emilia Johnson, Lara G. Moussa , Aidan Desjardins, Bárbara I. A. Xavier , Fabiana Almerinda G. Palma, Sara Macbride-Stewart, Federico Costa, Robert Dreibelbis, Max T. Eyre 

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.