Leptospirosis in Europe: climate change will raise the risk

Despite being less of a threat in Europe than in tropical areas, leptospirosis – a bacterial infectious disease – appears to be an emerging public health concern in Europe. A new study indicates that climate change is likely to increase disease incidence, expand geographic distribution, and lengthen the transmission season. 

The study is the first Europe-wide spatiotemporal modelling of leptospirosis risk, considering epidemiological data, and environmental and climate predictors. It offers key evidence to inform surveillance strategies, guide public health preparedness, and support targeted interventions addressing climate-sensitive infectious diseases that jump from animals to humans.

Caused by spirochetes of the genus Leptospira, Leptospirosis is a zoonotic disease transmitted from animals to humans, most commonly via the urine of infected rodents, but livestock and pets may also play an important role. Infection typically occurs through contact with contaminated water, soil, or food, especially after flooding events or in areas with poor sanitation. 

Trends in Europe

Between 2010 and 2023, a total of 3,930 leptospirosis cases were reported in Europe, corresponding to an average of approximately 281 cases per year. Around 140 NUTS 3 regions (of nearly 1200 in the EU) reported cases annually, and both the number of cases and the geographic spread showed a noticeable increasing trend over time.

Although leptospirosis incidence in Europe is relatively low compared to tropical regions, it still is a concern for a public health. The disease is often underdiagnosed and underreported, suggesting that the true burden is higher than reported figures indicate. 

Clinical outcomes can be severe, including multi-organ failure, with approximately 42% of confirmed cases requiring hospitalisation. Globally, leptospirosis accounts for around one million cases and approximately 60,000 deaths per year.

Role of climate factors

Climate variables play a key role in shaping leptospirosis risk. Higher temperatures and wetter conditions are associated with increased transmission. Elevated temperatures show a particularly strong effect, with risk increasing up to fivefold, while wetter conditions also contribute to higher incidence.

Over the study period, both the number of cases and the number of regions affected have increased. Changes in temperature, rainfall patterns, and extreme weather events influence environmental conditions, reservoir dynamics (rodent populations) and pathogen survival. Together these factors contribute to a growing and more dynamic risk of leptospirosis in Europe.

Future projections

Projections indicate that leptospirosis incidence is expected to increase in the future under all climate scenarios considered.  Increases are projected to be more moderate in the short term (2041–2060) and more pronounced in the long term (2081–2100).

The magnitude of change depends on greenhouse gas emission pathways. Under high-emission scenarios, the rise in incidence is significantly greater than under more moderate scenarios. Overall, approximately 70% of regions are projected to experience increases in disease incidence.

Climate change is also expected to extend the transmission season. While currently peaks occur in late summer, future increases are projected to affect winter and spring months as well, widening the temporal window of risk.

Territorial and seasonal distribution

During the 2010–2023 period, higher incidence rates were observed in warm coastal regions and densely populated areas. The disease showed strong seasonality, with 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 and expansion in the spatial distribution. Northern and central European regions historically characterised by lower incidence due to cooler climates, are likely to become more suitable for transmission. At the same time, localised decreases may occur in parts of southern Europe, where increasing temperatures and dryness could reduce bacterial survival.

Overall, the main trend is an expansion both geographically and seasonally, with more regions affected and risk extending into additional months of the year.

Recommendations

The study highlights the need for a combination of public health, environmental, and climate-related interventions.

From a public health perspective, strengthening surveillance systems is essential, along with improving diagnostic capacity and reporting. Integrating climate-informed early warning systems could help anticipate outbreaks and enable timely responses.

Environmental and urban measures are also important. These include improving water management, enhancing sanitation and drainage infrastructure, and implementing effective rodent control strategies.

At policy level, reducing greenhouse gas emissions is critical to limiting long-term increases in disease risk. Climate mitigation strategies should therefore be considered part of public health planning.

A One Health approach, integrating human, animal, and environmental data is also essential. Improved monitoring of animal reservoirs, particularly rodents, is necessary to better understand transmission dynamics.

Finally, increased investment in research and targeted awareness campaigns in high-risk areas will be essential to strengthen preparedness and reduce future disease burden.