A scoping review and thematic analysis of the effects of tropical cyclones on diarrheal diseases

Background: Tropical cyclones pose significant health risks and can trigger outbreaks of diarrheal diseases in affected populations. Although the effects of individual hazards, such as rainfall and flooding, on diarrheal diseases are well-documented, the complex multihazard nature of tropical cyclones is less thoroughly explored. To date, no dedicated review comprehensively examines the current evidence and research on the association between tropical cyclones and diarrheal diseases.

Methods: We performed a scoping review to map the literature on tropical cyclones and diarrheal diseases. A comprehensive literature search was performed across multiple online databases, including PubMed/MEDLINE, Web of Science, Scopus, Google Scholar, and ProQuest. We then performed a thematic analysis on the specific transmission pathways between tropical cyclones and diarrheal diseases as described in the literature.

Results: A total of 96 studies were included and categorized in this scoping review. Of these, 23 studies quantitatively assessed the association between tropical cyclones and diarrheal diseases, with more than half reporting a positive association. Additionally, we identified 30 studies that detailed transmission pathways, which we used for thematic analysis. Significant variability was observed in the definition of tropical cyclone exposure, with studies using different criteria such as an event, wind speed, or rainfall. Most studies used pre-post comparison designs without concurrent control groups, which can introduce limitations affecting internal validity by not accounting for temporal confounders. Diarrheal diseases can either increase or decrease during and after tropical cyclones, depending on the specific pathogens and the different strengths of tropical cyclones.

Conclusion: The variability in exposure definitions and study designs impedes the ability to quantitatively pool evidence. To improve the comparability and reliability of future research, we recommend that studies explore how different tropical cyclone exposure definitions impact results to identify the most appropriate metrics. We also suggest adopting more robust study designs, such as difference-in-difference or controlled interrupted time series for studying single tropical cyclone events, and case-crossover designs for studying multiple events. Additionally, studies examining specific causal pathways, such as integrating environmental sampling with health outcomes, should be explored to identify effective prevention strategies.