How is climate change fueling a global surge in diseases?

ISTANBUL

As extreme temperatures and natural disasters take a devastating toll on people across the globe, experts are also sounding the alarm over another way that climate change poses a threat to human lives: fueling a surge in both infectious and non-communicable diseases.

With last year being the warmest on record and 2024 already following suit with scorching heat, researchers are calling for more attention to the growing spread of diseases such as dengue, chikungunya, and malaria, which are largely transmitted by mosquitos.

Extreme climate events like floods, cyclones and droughts are also leading to a graver threat of other infectious diseases such as cholera.

Then there are non-communicable but fatal diseases, such as cardiovascular ailments and respiratory illnesses, which are also directly linked to the climate crisis.

The World Health Organization (WHO) has warned that climate change is “impacting health in a myriad of ways,” including deaths and illness from extreme weather events and “increases in zoonoses and food-, water- and vector-borne diseases.”

In the coming years, between 2030 and 2050, climate change is expected to cause 250,000 additional deaths every year, due to malnutrition, malaria, diarrhea, and heat stress, according to the UN agency.

Mosquitos on the move

Infectious diseases are defined as illnesses caused by pathogens, such as viruses, bacteria, fungi, and parasites that enter the body.

“Local manifestations of the warming earth, such as shorter winters, changes in precipitation, and increased frequency of extreme weather events, will cause worldwide changes in pathogens, vectors, and the behavior of animal reservoirs and people,” according to a study recently published in the medical journal JAMA.

The WHO has already documented a surge in dengue this year, a virus transmitted to humans through the bite of infected mosquitos.

By April, it reported receiving over 7.6 million dengue cases, including over 16,000 severe infections and more than 3,000 deaths.

The increase has been particularly significant in North and South America, where the number of cases had exceeded 7 million by the end of April, surpassing the annual high of 4.6 million in 2023.

Across the Atlantic, the European Center for Disease Prevention and Control (ECDC) has warned that climate change is creating more favorable conditions for invasive mosquitos to spread into previously unaffected areas and infect more people with diseases such as dengue.

The ECDC said the Aedes albopictus mosquito species, a known vector of chikungunya and dengue viruses, has spread “further northwards and westwards in Europe,” from 8 European countries and 114 regions in 2013 to 13 countries and 337 regions in 2023.

The Aedes aegypti mosquito, known to transmit dengue, yellow fever, chikungunya, Zika and, potentially, West Nile viruses, has also been found in Europe and “may continue to spread to other European countries,” the ECDC said.

According to WHO data, more than 2 million chikungunya disease cases have been reported in over 110 countries in Asia, Africa, Europe, and the Americas since 2005.

Latest ECDC figures showed around 320,000 chikungunya cases were recorded this year by the end of May, with more than 120 fatalities, in a total of 19 countries – 12 in the Americas, six in Asia, and one in Africa.

“Perhaps the clearest connection between climate change and infectious diseases that ECDC has observed is the one concerning the spread of mosquito-borne diseases,” Celine Gossner, principal expert for emerging and vector-borne diseases at ECDC, told Anadolu.

“We see that warmer climates create more favorable conditions for invasive mosquito species that can transmit diseases such as dengue and chikungunya, among others.”

She said there is some evidence to suggest that climate change may be contributing to the emergence or re-emergence of certain diseases.

“Europe is indeed experiencing a warming trend with more frequent hot spells, longer and warmer summers, and an increase in the frequency, duration and severity of heat waves and floodings,” she said.

“However, apart from changes in temperature, one should also consider factors such as increased precipitation and more frequent droughts.”

Climate change is one component of the global ecological crisis, Gossner explained, and its connections to other factors that impact infectious disease spread, such as travel and migration, land use and habitat changes, water accessibility and quality, should be understood and assessed in its complexity.

An article published earlier this year in medical journal The Lancet also confirmed that chikungunya virus outbreaks are “becoming increasingly common.”

“Driven by increased connectivity of communities and climate change, both the Aedes vector and the chikungunya virus are increasing their footprint. Regions, such as Europe and North America, that were historically free from the virus now regularly see local transmission,” read the article.

Too much heat for the human heart

Rising temperatures are also contributing to a spike in heat- and heart-related illnesses around the world.

Barrak Alahmad, a research fellow of environmental health at Harvard University, stressed that climate change is here and no longer a future risk, warning of its dire effects on human health.

“Our bodies have a limit. When it’s too hot, the heart will work harder to pump blood and meet the metabolic demand. We’re essentially putting the heart under stress. In individuals who already have existing heart disease, exposure to heat will heighten that risk,” he explained.

According to the academic, emerging evidence is now linking heat to increased risk of heart attacks, heart failure, ischemic stroke – caused by blockage in brain arteries – and hemorrhagic stroke, caused by a burst brain artery.

“We see the elderly and those with existing heart disease to be the most vulnerable. Additionally, the toll of heat falls more heavily on low-income and minority communities. We also see worst effects on immigrant workers that work outdoors under hazardous heat conditions,” he told Anadolu.

According to a WHO factsheet, heat-related deaths among people over age 65 increased by “approximately 85% between 2000-2004 and 2017-2021.”

“Between 2000-2019, studies show approximately 489,000 heat-related deaths occur each year, with 45% of these in Asia and 36% in Europe,” the WHO said, citing data from various sources.

“In Europe alone in the summer of 2022, an estimated 61,672 heat-related excess deaths occurred … In 2003, 70,000 people in Europe died as a result of a June-August (high-intensity heat wave) event. In 2010, 56,000 excess deaths occurred during a 44-day heat wave in the Russian Federation.”

Alahmad added that people in the Middle East are the most prone to heat-related heart diseases.

“The Middle East is one area where the rate of heating is moving very fast. Projections show an inevitable hotter near future, even if we are to curb all emissions today. The region will be vulnerable to extreme hot conditions,” he said.

This problem is not going away anytime soon, he said, emphasizing that “policymakers need to realize that this new climate is the reality of this generation and the next generations.”