While leptospirosis, a bacterial infectious disease, has historically posed a lesser threat in Europe compared to tropical regions, recent findings suggest it is becoming an increasingly pressing public health issue on the continent. A pioneering study has revealed that climate change is likely to escalate the incidence of this disease, broaden its geographic reach, and prolong the transmission season.
This study marks the first comprehensive Europe-wide spatiotemporal modelling of leptospirosis risk, integrating epidemiological data alongside environmental and climate predictors. The insights gained are invaluable for shaping surveillance strategies, enhancing public health preparedness, and devising targeted interventions for climate-sensitive infectious diseases that can be transmitted from animals to humans.
What Is Leptospirosis?
Leptospirosis is caused by spirochetes belonging to the genus Leptospira. It is a zoonotic disease primarily transmitted to humans through contact with the urine of infected animals, particularly rodents, although livestock and pets can also play significant roles. Infection typically occurs when individuals come into contact with contaminated water, soil, or food, especially following flooding events or in areas with inadequate sanitation.
Cases Rising Across Europe
Between 2010 and 2023, Europe reported a total of 3,930 cases of leptospirosis, averaging approximately 281 cases annually. About 140 NUTS 3 regions, out of nearly 1,200 in the EU, documented cases each year, with both the incidence and geographic spread demonstrating a notable upward trend over time. Although the incidence of leptospirosis in Europe remains relatively low compared to tropical regions, it is still a significant public health concern. The disease is often underdiagnosed and underreported, indicating that the true burden may be considerably higher than official statistics suggest.
Clinical outcomes can be severe, with multi-organ failure occurring in some cases; around 42% of confirmed cases necessitate hospitalisation. Globally, leptospirosis accounts for approximately one million cases and around 60,000 fatalities annually.
How Climate Change Is Fueling the Disease
Climate variables significantly influence the risk of leptospirosis. Elevated temperatures and increased precipitation are associated with heightened transmission rates. Notably, higher temperatures can amplify risk by up to fivefold, while wetter conditions also contribute to increased incidence. Over the study period, both the number of cases and affected regions have risen, driven by changes in temperature, rainfall patterns, and extreme weather events that alter environmental conditions, reservoir dynamics, particularly rodent populations, and pathogen survival. Collectively, these factors contribute to a more dynamic and escalating risk of leptospirosis in Europe.
What Experts Expect in the Coming Decades
Projections indicate that the incidence of leptospirosis is set to rise under all climate scenarios considered. In the short term (2041–2060), increases are expected to be moderate, but more pronounced changes are anticipated in the long term (2081–2100). The extent of these changes is contingent upon greenhouse gas emission trajectories; under high-emission scenarios, the rise in incidence is significantly more pronounced than in more moderate scenarios. Overall, approximately 70% of regions are projected to experience increases in disease incidence.
Moreover, climate change is likely to extend the transmission season. Currently, peaks in cases occur in late summer, but future projections suggest that the risk will also affect winter and spring months, thereby broadening the temporal window of vulnerability.
How the Disease Is Spreading Across Europe
During the 2010–2023 period, higher incidence rates were observed in warm coastal regions and densely populated areas, with strong seasonal peaks occurring in August and September. At present, the disease remains concentrated in southern and coastal regions, although its geographic distribution is gradually expanding. Future projections indicate a shift in spatial distribution, with northern and central European regions, historically characterised by lower incidence due to cooler climates, becoming increasingly conducive to transmission. Conversely, localized decreases may occur in parts of southern Europe, where rising temperatures and aridity could hinder bacterial survival. Overall, the principal trend indicates an expansion in both geographic and seasonal dimensions, with more regions becoming affected and the risk extending into additional months of the year.
Steps Experts Say Are Needed Now
The study underscores the urgent need for a multifaceted approach to address the challenges posed by leptospirosis.
From a public health standpoint, enhancing surveillance systems is paramount, alongside improving diagnostic capabilities and reporting mechanisms. Integrating climate-informed early warning systems can facilitate the anticipation of outbreaks and enable timely interventions.
Environmental and urban measures are equally critical. These include improving water management, upgrading sanitation and drainage infrastructure, and implementing effective rodent control strategies.
At the policy level, reducing greenhouse gas emissions is essential for mitigating long-term increases in disease risk. Therefore, climate mitigation strategies should be integrated into public health planning.
A One Health approach, encompassing human, animal, and environmental data, is also vital. Enhanced monitoring of animal reservoirs, particularly rodent populations, is necessary to gain a deeper understanding of transmission dynamics.
Finally, increased investment in research and targeted awareness campaigns in high-risk areas will be crucial for bolstering preparedness and reducing the future burden of disease.
In conclusion, as leptospirosis emerges as a growing public health concern in Europe, a concerted effort involving public health, environmental, and climate-focused interventions is essential to mitigate its impact and safeguard public health in an era of climate change.
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