Evolving climatic conditions yield novel susceptibilities for epidemic diseases
In a groundbreaking study published in Science Advances in 2025, researchers have shed light on the factors that increase the risk of zoonotic disease outbreaks, focusing on nine diseases with high potential to cause severe public-health emergencies, including Zika virus, Ebola, SARS, Covid-19, and others.
The study found that 9% of the world's land surface, home to around 130 million people, is at "very high" or "high" risk of outbreaks of these diseases. This risk is primarily related to environmental, anthropogenic, and climatic factors that influence the interactions between humans, animals, and their shared environments.
Key drivers of zoonotic diseases identified in the study include:
- Climate Factors: Warmer temperatures and increased rainfall can favor pathogen survival and vector populations, such as mosquitoes and ticks. Water scarcity also influences animal behavior, leading to more concentrated interactions among animals and humans around limited water sources, promoting spillover events.
- Environmental and Land-Use Changes: High livestock density near human settlements increases infectious pressure. Deforestation, habitat fragmentation, and land-use changes bring humans closer to wildlife reservoirs, escalating the chances of human-wildlife pathogen spillover.
- Population Density and Urbanization: Rapidly growing, dense populations, especially in unplanned urban areas with poor infrastructure, heighten direct and indirect contact between humans and animals, facilitating outbreaks.
- Human-Animal Interaction: Closer and more frequent contact between humans and animals (domestic, wild, or livestock) increases transmission risk. This includes direct contact, exposure to infected animals or their waste, and contact with vectors like ticks or mosquitoes.
- Animal Health Status and Reservoirs/Vectors: Animals that harbor pathogens or transmit them via bites or other contact routes play a critical role in zoonotic transmission.
Globally, these factors concentrate risk unevenly, with hotspots of zoonotic threat identified especially in Latin America, Oceania, Asia, and Africa. About 3% of the world’s population live in high-risk areas, with an additional 20% in medium-risk zones.
The study also developed an "epidemic risk index" which shows each country’s risk and capacity to respond to "zoonotic threats". In this index, Papua New Guinea is ranked as the lowest - indicating the greatest risk of epidemics.
The research warns that climate change is creating new vulnerabilities for zoonotic disease transmission as it reshapes the geographic distribution of risk. Higher temperatures, increased rainfall, water scarcity, and changes in land use are identified as key drivers of disease outbreaks.
However, the study received mixed responses from scientists not involved in the work. While some praised its holistic perspective and innovative methodology, others criticized its focus on tropical ecosystems and argued that poverty plays a larger role in disease outbreaks.
Despite these debates, understanding and managing these drivers are essential for predicting and preventing emerging zoonotic disease outbreaks globally. As the number of new zoonotic diseases continues to rise, it is crucial to remain vigilant and proactive in our efforts to protect public health.
- The study published in Science Advances in 2025 reveals that climate change is generating new vulnerabilities for zoonotic disease transmission, largely due to factors such as warmer temperatures, increased rainfall, and water scarcity.
- In the groundbreaking study, researchers found that deforestation, habitat fragmentation, and land-use changes bring humans closer to wildlife reservoirs, heightening the risk of human-wildlife pathogen spillover, a key factor in zoonotic disease outbreaks.
- The study also emphasized the importance of effective water security in preventing zoonotic disease outbreaks, as water scarcity influences animal behavior, leading to increased contact among animals and humans around limited water sources.
- The research highlights the role of environmental science and medical-conditions in identifying and addressing the drivers of zoonotic disease outbreaks, with an aim to improve health-and-wellness by predicting and preventing emerging diseases.
- Globally, the study indicates that climate change, deforestation, and changes in land use are primary drivers of zoonotic disease outbreaks, with hotspots of zoonotic threat identified in Latin America, Oceania, Asia, and Africa.
