Climate Change and Diarrhoeal Disease in Homa Bay County, Kenya: An Analysis of Impact, Vulnerability and Adaptation

Purpose: This study investigated the relationship between climatic factors (temperature, rainfall, humidity) and diarrhoeal disease incidence in Homa Bay County, Kenya, while assessing household exposure, sensitivity, and adaptive capacity to inform policy. Methodology: A mixed-methods approach combined ecological time-series analysis and household surveys. Climate and morbidity data (2010-2024) were analysed alongside primary data from 401 households, collected using structured questionnaires. Findings: Autoregressive Lag models estimated short and long-run climate effects on diarrhoeal, while logistic regression assessed household vulnerability. Mean monthly diarrhoeal cases were 4,041 (SD = 12,285), with average temperature 23.3°C (SD = 1), rainfall 117.7 mm (SD = 67), and relative humidity 74%. The long-run model indicated strong persistence, with a highly significant first lag (IRR = 1.514). Temperature showed lag-dependent effects, with early lags positive and a negative effect at the third lag. Rainfall exhibited a delayed influence, with the third lag marginally significant (IRR = 1.061), while humidity had a strong negative association at the third lag (IRR = 0.471). Short-run dynamics showed significant autoregression, with the first lag of diarrhoeal positive (IRR = 1.330). Household sensitivity, linked to older household heads, low education, poor housing, and climate-exposed livelihoods, increased diarrhoeal odds by 78%, while flood-related exposure contributed to outbreaks. Unique Contribution to Theory, Practice and Policy: The findings of this study demonstrate that long-term variations in rainfall and humidity, when combined with structural public health interventions, play a decisive role in shaping the steady-state levels of diarrhoeal disease incidence. Consequently, effective diarrhoeal prevention strategies should prioritize reducing household sensitivity while enhancing adaptive capacity and water infrastructure, sanitation, and hygiene systems.