Climate crisis or health emergency? WMO links rising heat to dengue surge

As heat intensifies, dengue is spreading faster and reaching new regions, with climate change reshaping transmission patterns and increasing global health risks

The past decade (2015-25) has been the hottest ever recorded, according to the World Meteorological Organization’s State of the Global Climate 2025 report. This sustained rise in temperatures is no longer just an environmental concern and is increasingly influencing how diseases emerge and spread. 

Dengue, once largely confined to certain tropical regions, is now expanding its footprint at an alarming rate. The report highlights how rising heat is intensifying both the spread and severity of outbreaks, while shifting climate patterns and more frequent extreme weather events are creating conditions that favour transmission. As a result, the impact of warming temperatures on global health is becoming more visible and more difficult to ignore.

 

 

Heat and dengue: A dangerous link

 

The global rise in dengue cases reflects how closely the disease is tied to climate. Around 14.4 million cases were reported in 2024, the highest ever recorded, and the infection is now spreading into new regions and higher altitudes where it was once rare. At the same time, transmission seasons are becoming longer and less predictable, driven by rising temperatures and shifting rainfall patterns, which together are worsening the scale of outbreaks.

 

A 2025 study published in the BMC Public Health journal revealed that a 1°C rise in temperature can increase dengue infection risk by 13 per cent. The virus replicates fastest between 32°C and 35°C, making hot conditions ideal for spread. Warmer climates speed up mosquito breeding and biting rates, while also shortening the virus incubation period inside the mosquito.

 

Together, these changes mean that heat does not just increase mosquito numbers, but also makes each mosquito more efficient at transmitting the virus, amplifying the intensity and spread of outbreaks.

 

Climate shifts expanding risk zones

 

According to the World Health Organization (WHO), dengue has expanded dramatically over the past five decades, spreading from fewer than 10 endemic countries in the 1970s to more than 130 today. The highest burden is seen across Latin America, Asia and parts of Africa. Rapid urbanisation, inadequate water and waste management, and increased mobility have enabled the spread of Aedes mosquitoes, while climate variability has pushed transmission into some temperate regions.

 

• Increased rainfall and humidity lead to more stagnant water, which supports mosquito breeding
• Milder winters allow mosquitoes to survive in previously cooler regions
• Urbanisation and poor waste management create micro-environments for mosquito growth

 

As a result, more than half the global population now lives in areas at risk of dengue infection, and regions that once saw sporadic cases are now reporting sustained outbreaks.

 

Chronic and extreme heat stress: A parallel crisis

 

The WMO report also flags a broader health emergency linked to rising temperatures. Exposure to heat is rising steadily, with people in some regions experiencing hundreds of additional hours of heat stress each year. Over time, this prolonged exposure leads to chronic heat stress, which can weaken immunity and increase vulnerability to infections.

 

The impact is especially visible in the workforce, where over one-third of people globally, around 1.2 billion, face heat-related risks at work each year, particularly those working in sectors like agriculture and construction. Higher temperatures are also driving fatigue, dehydration, injuries and kidney strain, while affecting mental health and reducing productivity and livelihoods.

 

Why this matters

 

The intersection of climate and health is no longer theoretical, and dengue is emerging as one of the clearest examples of how warming temperatures translate into real-world disease risks.

 

• Heatwaves are becoming more frequent and intense, especially in tropical countries
• Health systems in many regions are not equipped for climate-driven outbreaks
• Vulnerable populations, including children, the elderly, and outdoor workers, face disproportionate risk
• Climate-sensitive diseases are expanding faster than surveillance and response systems can adapt

 

What needs to be done

 

Experts say there is a need for heat-aware planning and policies, especially stronger workplace safety measures, to better protect workers from rising temperatures worldwide.

 

• Strengthen early warning systems linking weather and disease surveillance
• Scale up vector control measures, especially in hotspots
• Improve public awareness on preventing mosquito breeding
• Build heat-resilient health systems to manage both heat stress and infectious diseases

     

For more health updates, follow #HealthwithBS

This report is for informational purposes only and is not a substitute for professional medical advice.