World Health Organization Says Extreme Heat Overwhelms Thermoregulation, Threatening Health In Europe

The World Health Organization (WHO) says extreme heat is a growing health threat, and it frames climate change as a driver of worsening conditions that can “pose an increasing risk to human health by causing deaths and suffering, and by overloading health systems around the world.”

In WHO’s account of summer health risks in the European Region, the organization ties the danger to how the human body regulates temperature, noting that the body maintains a core temperature of about 37°C and cools itself by sweating when outside temperatures rise.

CNN

WHO warns that “prolonged exposure to extreme heat is a source of suffering, affects mental health and well-being, and can ultimately overwhelm this natural thermoregulation mechanism.”

It also emphasizes that the impact is not uniform, singling out older people, infants and young children, and outdoor workers such as farmers, construction workers, and emergency service personnel, including firefighters.

WHO further links extreme temperatures to worsening chronic conditions, naming cardiovascular diseases, respiratory diseases, and diabetes, and it adds that pregnant women face higher risk because extreme heat is linked to pregnancy complications such as premature births and low birth weight.

To address the risk, WHO/Europe promotes the annual campaign “#Gardezlatêtefroide,” which it describes as delivering “simple and practical advice” so individuals and communities can protect themselves during hot weather.

The WHO guidance also lays out specific steps, including “Avoid heat” during the hottest hours, “Keep your indoors cool,” “Hydrate and refresh your body,” and “Stay in touch” with family, friends, and neighbors who may need help.

A separate science-policy framing from Perry World House (PWH) places extreme heat and other hazards inside a broader health risk picture, describing climate change as “the single biggest health threat facing humanity.”

PWH says warming is “approximately 1.14°C above preindustrial levels” and that the Intergovernmental Panel on Climate Change (IPCC) predicts “with very high confidence that climate-related illness will also rise.”

UC Davis

It argues that “policy has not kept pace,” and it calls for “future-proof public health against the impacts of warming that, much like threats to public health, have no territorial bound.”

In PWH’s account, severe weather—including “droughts, floods, heatwaves, wind, and wildfires among them”—is expected to occur “with greater frequency and intensity,” threatening human well-being.

PWH also ties these hazards to the vulnerability of health infrastructure, describing small islands and low-lying territories where “critical infrastructure, like hospitals, is in close proximity to shorelines and therefore vulnerable to storm and tidal surges.”

The convening described by PWH, held “on 14 April 2026” on the margins of the International Monetary Fund and World Bank Spring Meetings, is presented as an attempt to “bridge the science-policy gap” for climate-driven determinants of health.

PWH says participants discussed why climate change is a “threat multiplier to planetary health,” and it highlights impacts on “human physical and mental well-being, healthcare infrastructure, and animal health.”

It also connects climate shifts to infectious disease risk, noting that “unpredictable rains and changing monsoon seasons are threatening food security while also creating breeding grounds for mosquitoes that host infectious diseases like dengue and chikungunya.”

Perry World House’s recommendations emphasize a One Health approach and integrated surveillance as a way to move from reactive measures to readiness, recommending “a One Health approach” that emphasizes “the interdependence of animal, human, and environmental health.”

“Climate change is likely to drive rodent-borne arenaviruses into parts of South America that have never faced these diseases, putting new communities of people at risk, finds a study from the University of California, Davis”

UC Davis

It says this framework could be “particularly effective for addressing antimicrobial resistance and zoonotic diseases through the ‘integrated surveillance’ of humans, animals, and the environment.”

PWH also calls for “Preventive systems” that focus on “early warning signs for both humans and animals to save lives and protect infrastructure,” and it describes local implementation as “community response systems and the training of local providers to ensure a state of readiness before disasters occur.”

In the same policy framing, PWH argues that “Nations require science diplomacy” to bridge the gap between medical research and policy, and it says political leadership should map “specific community health risks” and build “technical capacity for health systems to respond to climate shocks.”

It also says academia can support policy by building infrastructure for data collection and providing “evidence-based interventions,” and it points to integrating climate and health education into school curricula.

The science-policy emphasis on early risk projection is echoed in UC Davis research on rodent-borne arenaviruses, where scientists “incorporated climate projections, shifting rodent populations and the risks of human infection into a model to offer an early risk projection for arenaviruses and other diseases in the next 20 to 40 years.”

UC Davis reports that arenaviruses can cause “severe hemorrhagic fevers with high hospitalization rates and fatality rates ranging from about 5% to 30%,” and it describes how the team built an interactive, open-source platform called AtlasArena with funding from Wellcome Trust.

UC Davis describes climate change as likely to “drive rodent-borne arenaviruses into parts of South America that have never faced these diseases,” creating risk for “new communities of people.”

The study, published in the journal npj Viruses, is presented as combining climate projections with rodent population shifts and human infection risk, and it uses the open-source AtlasArena platform to understand “climate change is reshaping the risk of zoonotic spillover for arenaviruses and other hard-to-track viruses.”

CNN

Lead author Pranav S. Kulkarni, a postdoctoral scholar in the UC Davis Weill School of Veterinary Medicine and its Department of Population Health and Reproduction, is quoted saying, “As climate change accelerates, our study shows how the outbreak risk of dangerous New World arenaviruses could ride on shifting rodent populations to reach millions more people across South America.”

UC Davis identifies New World arenaviruses including Guanarito virus in Venezuela and Colombia, Machupo virus in Bolivia and Paraguay, and Junin virus in Argentina, and it contrasts them with Old World arenaviruses such as Lassa fever in Africa.

The report says the risk of spillover is “primarily driven by changes in temperature, precipitation and land use, such as expanding agricultural and urban areas within rodent reservoir habitats.”

It also provides specific model projections: Guanarito virus is expected to spread to parts of Colombia, the borders of Suriname and northern parts of Brazil; Machupo virus is expected to move from Bolivia’s plains and flatlands to the Andes foothills and mountain regions; and Junin virus is expected to move from grassland regions to other parts of Argentina.

UC Davis adds that “in all cases, populations with little or no prior exposure would be encountering these viruses for the first time,” potentially increasing vulnerability to infection and severe disease.

Senior author Pranav Pandit, an assistant professor of veterinary epidemiology at the UC Davis Weill School of Veterinary Medicine, is quoted explaining, “Our study connects the dots between changing climatic conditions and land use, shifting rodent populations and human infection risk, making it possible to see where the next generation of zoonotic arenaviral outbreaks could emerge.”

The study’s authors say the results underscore “an urgent need for coordinated climate-adaptive public health policies and transboundary collaboration among countries at risk,” and they describe how the AtlasArena platform is “freely available” and can be adapted to study other climate-sensitive diseases.

WHO’s heat guidance and Perry World House’s policy framework both point toward coordinated action, but they do so through different lenses: WHO/Europe emphasizes practical measures and heat-health action plans, while Perry World House emphasizes integrated surveillance and science-policy bridging.

WHO says “National and local heat action plans protect public health,” and it describes how developing such plans “brings together actors from multiple sectors to better manage heat-related risks.”

UC Davis

It states that these plans “define roles and responsibilities during extreme heat episodes, integrate early warning systems, identify vulnerable populations, and establish communication and intervention mechanisms,” and it adds that WHO/Europe is “currently updating its recommendations on heat-health action plans to provide stronger support to member states.”

Perry World House similarly argues that “political leadership should focus on practical steps,” including mapping “specific community health risks” and building “technical capacity for health systems to respond to climate shocks,” and it says “Nations require science diplomacy” to bridge the gap between research and policy.

In its description of convening participants, PWH says the session drew representatives from Maldives, France, Germany, and Italy, and it frames the discussion as bridging “the science-policy gap” to inform responses to climate change impacts on health.

The UC Davis study’s call for coordination aligns with this, stating that the results underscore “an urgent need for coordinated climate-adaptive public health policies and transboundary collaboration among countries at risk.”

The CNN piece adds a communications and data-cooperation angle by centering WHO Europe’s Dr. Hans Henri Kluge, who is described as explaining “how climate change is driving health risks and why stronger data and cooperation are needed to prevent local outbreaks becoming global emergencies.”

Across the accounts, the common thread is that climate-related health threats require both immediate protective steps—like WHO’s “Avoid heat” and “Hydrate and refresh your body”—and longer-term systems that integrate early warning, surveillance, and cross-sector coordination.