Effects of the 2018 European summer heatwave on the incidence of sporadic bacterial gastroenteritis in a temperate maritime climate region (Republic of Ireland)

Background: The IPCC recognises that climate change and associated extreme weather events (EWEs), including heatwaves, will incur negative human health impacts. In Ireland, projections indicate more frequent and severe EWEs, however, research on the health impacts of heatwaves in temperate regions is still in its infancy. Purpose/aims/objectives: We aimed to analyse the spatiotemporal characteristics of two bacterial infections (STEC enteritis and campylobacteriosis) to quantify the public health effects of the 2018 European summer heatwave in Ireland. Materials and methods: Additive decomposition and Interrupted Time-Series Analyses (ITSA) were used to quantify effects. Excess weekly cases were calculated based on pre/post-event conditions across several case delineations (e.g., gender, age, serotype and settlement pattern. Results: Findings suggest that the summer 2018 heatwave was responsible for a minimum of 169 excess case notifications of campylobacteriosis (n = 101) and STEC enteritis (n = 68). Heatwave effects were immediate (i.e., within 10 days, p = 0.0019) on campylobacteriosis cases. Significant increases were observed among males, younger adults, and urban residents. STEC enteritis notification did not immediately change, but lagged effects (≥4 weeks, p < 0.001) were noted, with significant case notification increases identified among older adults (>65 years) and rural dwellers, alongside a notable increase in STEC O26 cases (p = 0.026). Conclusions: Conditions during the 2018 European summer heatwave facilitated increased case numbers of STEC enteritis and campylobacteriosis across Ireland, in concurrence with shifting demographic and geographic transmission patterns. With climate change likely favouring bacterial proliferation, further increases and pattern shifts are expected.