The world is facing an increasing frequency and severity of epidemics and pandemics caused by the transmission of pathogens from animals to humans, known as zoonotic transmission. These events have potentially serious consequences for human health. The scientific literature identifies five main groups of anthropogenic factors that influence the risk of zoonoses: climate change, human population dynamics, livestock farming, agricultural intensification, and biodiversity loss. The new study comprehensively examines the common drivers of zoonotic diseases with epidemic and pandemic potential, among which climate conditions play a key role.

Key climate factors increasing disease risk

The World Health Organization's (WHO) analysis of common drivers of priority diseases suggests that climate conditions directly increase the risk of disease outbreaks. These factors include:

• Higher temperatures: The study confirms that Consistently warmer areas with higher maximum and minimum temperatures are more prone to disease outbreaksThis finding is crucial because, as the planet warms unevenly, even cooler regions may eventually reach conditions suitable for the spread of these diseases. Infectious diseases generally thrive better in warmer temperatures.
• Higher annual precipitation levels: Our study shows that higher annual precipitation levels may increase the risk of disease outbreaks to some extent, after which the risk levels off. This is expected, particularly in tropical regions where these diseases are common and rainfall levels are typically high. Increased rainfall is associated with a higher risk of vector-borne diseases affecting both humans and animals.
• Water deficit: Annual summaries of temperature and precipitation fail to adequately capture the impact of intraocular water availability on disease risk. The analysis includes a water deficit index, which represents the cumulative monthly differences between precipitation and potential evapotranspiration. Model results show that The risk of outbreak is closely related to the level of water deficit, but not linearly. The highest risk occurs in areas with a medium level of water deficit index. Lack of water and vegetation leads to the concentration of animals (both wild and domestic) around limited water and food sources, facilitating the transmission of pathogens. During periods of resource scarcity, animals may encroach on human settlements, particularly when water scarcity coincides with irrigation systems, increasing the likelihood of contact between human populations, livestock, and wild animals, and consequently increasing the risk of transmission.

Climate change affects disease risk, including vector-borne diseases such as Rift Valley Fever and Zika, and non-vector-borne diseases such as Ebola, which are affected by climate change through impacts on fruit abundance, attracting bats and increasing the chance of people coming into contact with infected reservoirs. Extreme weather events, forest fragmentation and deforestation can also increase the risk of disease transmission such as Lassa fever.

A comprehensive approach to risk assessment

Study also highlights the key role of environmental and sociodemographic factors. For example, higher human population growth and population density contribute significantly to the overall risk of disease outbreaks, exceeding the contributions of other individual factors. Land-use changes and human encroachment into forested areas also increase the risk.

A global risk map and epidemic risk index have been developed to provide a comprehensive threat assessment. This index combines the specific risk of countries with their capabilities to prepare for and respond to zoonotic threats. It is emphasized that Although some countries show a linear relationship between outbreak risk and epidemic risk, others can reduce their risk through effective zoonotic response capabilities.This underlines the importance of response capacity in mitigating risk.

Conclusion and challenge for the future

Climatic factors are key drivers of disease outbreaks, with climate change creating new vulnerabilities as it reshapes the geographic distribution of risk. These findings highlight the need for continued monitoring and integration of climate change adaptation and mitigation efforts into public health planning.

Think of climate change as a change in the weather for the home of viruses and bacteria. When the weather changes – for example, it gets warmer, rains more, or there are periods of drought – they suddenly form ideal conditions for "pests" (pathogens) and "carriers" (animals, insects)These new conditions allow them to reproduce more easily, move to new places, and come into contact with people more often, thus increase the likelihood that the "house" (our health) will be attacked by diseases. Spring

A study published in the journal Science Advances