Last summer, many European cities broke temperature records.
This summer, we are seeing the same headlines again.
But for epidemiologists, a heatwave is not simply a weather event. It is a public-health challenge — one that is becoming more important every year.
In fact, heatwaves are among the deadliest natural hazards worldwide. Unlike floods or earthquakes, their impact is often invisible. People rarely die from heat alone. Instead, extreme temperatures worsen existing cardiovascular, respiratory, and kidney diseases, increasing the risk of hospitalization and death.
This means that the true impact of heat is often underestimated.
So how do epidemiologists measure it?
One common approach is to calculate excess mortality: comparing the number of deaths during a heatwave with the number that would normally be expected for the same period.
This method revealed the enormous impact of the 2022 European heatwaves. According to a study published in Nature Medicine, more than 61,000 heat-related deaths occurred across Europe that summer.
Not everyone faces the same risk.
Particularly vulnerable groups include:
• older adults
• people with chronic diseases
• infants and young children
• outdoor workers
• people living in densely populated urban areas
Cities can become significantly hotter than surrounding regions because of the so-called urban heat island effect: asphalt, concrete, and limited green spaces trap heat and reduce nighttime cooling.
As climate change increases the frequency and intensity of extreme heat events, public health systems are adapting.
Many countries now have:
✔ heat-health warning systems
✔ public cooling centers
✔ early warning messages
✔ targeted support for vulnerable populations
Heat is not just a question for meteorologists.
It is increasingly a question for epidemiologists, clinicians, urban planners, and policymakers alike.
Because understanding who is at risk — and why — is the first step toward preventing avoidable deaths.
#epidemiology #publichealth #climatechange #heatwave #urbanhealth #globalhealth