Climate and Environment Influence SFTS Risk in Humans and Animals

Mathematical models and recent analyses indicate that meteorological and environmental factors such as temperature, precipitation, atmospheric pressure, forest cover, and human mobility play a central role in the risk of Severe Fever with Thrombocytopenia Syndrome (SFTS) outbreaks in humans and animals. Integrating these data allows anticipation of high-risk areas and periods, guiding surveillance and response actions in a One Health approach.

SFTS is a zoonotic disease mainly transmitted by ticks, with high lethality and growing geographic expansion, especially in East Asia. The increase in case numbers and emergence in new areas have been attributed to environmental, climatic, and social changes. According to Yan and colleagues, between 2013 and 2025, 1237 cases of SFTS were reported in Japan, highlighting the growing importance of the issue for public health.

Recent studies detail how environmental and meteorological variables affect SFTS risk. Yan and colleagues identified that the disease risk follows an inverted U-shaped relationship with temperature and precipitation: maximum risk occurs at 21.8°C (relative risk of 1.78) and 156.6 mm of weekly rainfall (relative risk of 1.30). High atmospheric pressure (up to 1027.1 hPa, relative risk of 2.06) and greater forest cover (up to 84%, relative risk of 6.58) also increase risk. Conversely, higher altitude areas showed reduced risk, with a risk peak at a mean altitude of 45 meters (relative risk of 3.99).

In Zhejiang, China, Yang and colleagues showed that mountainous and agricultural regions with moderate temperatures, high precipitation, and greater sun exposure concentrate more cases. Urbanization reduces risk, while human mobility increases SFTS incidence. According to Yang and colleagues, projections suggest a 23% increase in cases by 2028, with the transmission season expanding to year-round and 9% more municipalities reporting cases for the first time.

Lou and colleagues emphasize that tick abundance, modulated by local climate, is a key determinant for SFTS transmission. The study identified a shift in the disease's incidence peak from July to May in endemic areas since 2021, indicating that climate changes may bring forward and extend the risk period. Additionally, patients in areas with higher tick abundance have a greater risk of death, highlighting the importance of ecological monitoring.

The advancement of mathematical models allows prediction of SFTS risk based on environmental and meteorological data, even with limited information. Breda and colleagues developed a model that uses only human incidence and local temperature data to predict outbreaks, without prior assumptions about case behavior. According to the authors, including detailed ecological variables did not improve the model's predictive ability, suggesting that essential data already capture the main risk determinants.

These approaches provide tools to anticipate high-risk areas and periods, facilitating resource allocation and planning of public and veterinary health actions. Integration between environmental, meteorological, and epidemiological surveillance is fundamental for faster and more efficient responses.

Despite advances, the studies have limitations. Yan and colleagues point out that the associations identified are based on province-aggregated data, which may mask local variations. Yang and colleagues note that after including human mobility, random spatial effects did not improve the models, suggesting that other social factors still need to be better understood. Breda and colleagues acknowledge that data-driven models may prioritize predictive accuracy over transparency of biological mechanisms, which can limit detailed understanding of transmission processes.

Furthermore, projections depend on the maintenance of current climatic and behavioral trends and may be affected by interventions, unexpected environmental changes, or adaptations of vectors and hosts.

The analyzed studies indicate that incorporating environmental, meteorological, and social data into surveillance systems can anticipate SFTS outbreaks and guide prevention strategies in humans and animals. Integrated surveillance enables identification of critical areas and periods, adjustment of educational campaigns, targeted vector control, and monitoring of animal and human populations at risk. The projected increase in SFTS incidence and geographic distribution reinforces the need for continuous adaptation of public and veterinary health strategies in the face of environmental and social changes.

In summary, a deeper understanding of the relationship between climate, environment, and social dynamics with SFTS provides valuable input for One Health policies, highlighting the importance of integrating environmental, epidemiological, and veterinary surveillance to address emerging challenges of vector-borne diseases.