Heatwaves: Develop ‘Urban Heat Maps’ to Protect the Vulnerable says WHO
Informal neighbourhood on the periphery of Lima, Peru during a heat wave in April 2022. Vast areas of concrete and tin roofs exacerbate the urban heat island effect.

Mayors and other municipal officials should develop “urban heat maps” to identify and protect those most vulnerable to high temperatures, World Health Organization (WHO) official Maria Neira urged on Wednesday.

Many people in urban areas stifling under heat waves cannot afford cooling systems while conditions for outdoor workers not protected by legislation have become dangerous, added Neira, WHO Director of Public Health, Environmental and Social Determinants of Health.

She told the WHO’s weekly media briefing that people needed to be educated to recognize the signs of heat exhaustion and heat stroke.

Dr Maria Neira, director, Climate, Health & Environment.

Fulfilling early predictions, July has now been confirmed as the hottest month on record globally. It was 0.33°C warmer than the warmest month previously recorded in July 2019 and 0.72°C warmer than the 1991-2020 average for July, according to the European Commission’s Copernicus Climate Change Service.

While both urban and rural dwellers are affected by heat waves, typically, temperatures in cities can be 5-8° C higher than those in surrounding rural areas due to the . 

El Niño to heat world further

Surface air temperature anomaly for July 2023 relative to the July average for the period 1991-2020.

Meanwhile, the confirmation of an El Niño weather event by the World Meteorological Organization (WMO) last Friday is expected to further exacerbate the earth’s climate-change-related heating.

El Niño is a naturally occurring climate pattern that happens roughly every seven years when the warming of the ocean’s surface in the central and eastern tropical Pacific causes disruptive weather in far flung regions of the world.

“The onset of El Niño will greatly increase the likelihood of breaking temperature records and triggering more extreme heat in many parts of the world and in the ocean,” Petteri Taalas, WMO’s Secretary-General, said in a statement last Friday. 

“The declaration of an El Niño by WMO is the signal to governments around the world to mobilize preparations to limit the impacts on our health, our ecosystems and our economies,” Talaas warned. 

“Early warnings and anticipatory action of extreme weather events associated with this major climate phenomenon are vital to save lives and livelihoods.”

Mosquito-borne illnesses

Dengue virus, one of the best-known arboviruses, has resurged in the past several decades, becoming a major risk factor in cities, where infected mosquitoes breed in containers of stagnant water.

The increase in temperature and shifting rainfall has already seen a change in disease patterns – with extremely high rates of mosquito-borne dengue in the Americas – as well as warnings of  a  risk of possible dengue cases in Europe.

The warmer temperatures are allowing the Aedis aegypti mosquito, which transmits dengue, to thrive for longer periods and extend their mating season, allowing the mosquitoes to reproduce in greater numbers. 

However, Mike Ryan, the WHO’s executive director of health emergencies, warned that the behaviour of the Aedes aegypti mosquito and the Anopheles mosquito, which is a leading vector of malaria, are different and needed to be tackled differently.

The Aedes mosquito, which also transmits yellow fever and chikungunya, is active during the day whereas the Anopheles mosquito is active in the evening.

Mike Ryan, executive director of WHO Health Emergencies.

“The intervention we have in place for preventing malaria in kids is very often bed nets, but it doesn’t work as effectively when the mosquito transmitting the virus is biting during the day,” said Ryan, adding that Aedes aegypti breed in still water rather than rivers.

“Climate change is changing the zones in which these mosquitoes can survive and breed. Its changing characteristics are associated with the virus itself”, Ryan added 

“It’s changing human behaviour. It’s changing human migration. So what climate is doing is driving all of those factors in a way that’s very unpredictable and the outcomes we can’t predict very well,” he said.

Addressing the causes of climate change

Expansion of extremely hot regions in a business-as-usual climate scenario. Black and hashed areas represent unliveable hot zones. Absent migration, that area would be home to 3.5 billion people in 2070.

Meanwhile, the WHO’s COVID-19 lead, Maria van Kerkhove, stressed that countries need to use the systems developed over the past three years during the pandemic to address climate-related health challenges.

“Countries have worked incredibly hard to build those systems and strengthen systems for COVID. But those could also be used for other diseases,” she said, also speaking at the briefing. 

And Sylvie Briand, WHO’s Director of Epidemic and Pandemic Preparedness and Prevention, added that member states should use the Health Emergency Preparedness and Response Framework to address emerging diseases and new threats.

The framework was based on “the five C’s”, added Briand.These are collaborative surveillance, community protection, clinical care, access to countermeasures, and coordination.

Ahead of the upcoming UN Climate Change Conference (COP28) to be held in Dubai in December, Neira said the international community needs to focus more on preparing health systems to cope and adapt. “In addition, we need to look at mitigating the causes of climate change.” 

She said health and finance ministers will be invited to COP28 to discuss resources that will be required  “to be better prepared to cope with issues such as an increase of 35% in the population at risk of dengue in Southeast Asia, or at risk of malaria in places where we didn’t see it before.

“We [also] need to protect against the horrible consequences of air pollution ,which is killing seven million people every year; more sustainable…food systems, and of course better planning at the urban level,” she said warning:

“Climate change is already here.”

Image Credits: Paula Dupraz-Dobias, Copernicus Climate Change Service/ECMWF, PNAS.

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