In 2023, the world experienced the highest global temperatures in 100,000 years, with heat records broken on every continent. Warming is expected to continue, a change that currently appears irreversible and will cause extreme weather and climate events that will have significant socioeconomic repercussions on all inhabited continents.

It is not future but present. Almost a third of the global population is already exposed to deadly heat waves and the global land area affected by extreme droughts increased from 18% in the period 1951-1960 to 47% between 2013 and 2022, endangering not only water security , but also sanitation and food production.

With this panorama, it is estimated that between 3,300 and 3,600 million people live in contexts highly vulnerable to climate change and that the extinctions of animals and plants will increase profoundly in the coming decades. Furthermore, predictions suggest that by 2030, climate change will cause direct damage to health systems, causing an estimated loss of between $2 billion and $4 billion.

What’s more, forecasts predict that between 2030 and 2050, climate change will claim the lives of an additional 250,000 people per year due to malnutrition, heat stress, and an increase in zoonoses and food-, water-, and vector-borne diseases. .

In Europe, environmental conditions lead to an increase in tick-borne diseases

In this sense, the 2024 European report of The Lancet Countdown, which brings together more than one hundred leading experts on health and climate change, points out that, on the European continent, the suitability of environmental conditions has improved for various pathogens and vectors of climate-sensitive diseases, thus increasing the risk in Europe of the appearance of outbreaks caused by bacteria of the genus Vibrio, West Nile virus, dengue, chikungunya, Zika, malaria or leishmaniasis. Likewise, it promotes the activity of ticks that carry multiple pathogens such as those that cause Lyme disease, tularemia, tick-borne encephalitis (TBE), babesiosis, Colorado tick fever, theileriosis, the disease Heartland virus, Rocky Mountain spotted fever, rickettsiosis, human granulocytic anaplasmosis, and Crimean-Congo hemorrhagic fever, among many others.

For example, as a result of climate change, the number of favorable months for Ixodes ricinus ticks (the vector of Lyme disease and tick-borne encephalitis) has increased in Western Asia and Eastern Europe, a trend increasing for other tick species.

This amplifies exposure to the vector and implies the possible transmission of associated pathogens. In fact, various mathematical models clearly support the assumption that several tick species will benefit from climate change and expand their distribution over wide areas of Europe.

More dengue and leishmaniasis

As if that were not enough, all the current conditions in Europe favor the local transmission of dengue, especially in the south of the continent. These conditions include the presence of a suitable mosquito vector (Aedes spp.), a suitable group of people with the presence of the virus in their blood, and climatic conditions conducive to both the survival of the insect and the development of the virus in the vector. The scenario could be similar for chikungunya and Zika.

To make matters worse, multiple studies have shown that variations in temperature, precipitation and humidity affect the transmission and distribution of infectious diseases. For this reason, leishmaniasis, a climate-sensitive zoonotic disease caused by parasites of the genus Leishmania and transmitted by the bite of infected female sandflies, is expected to increase in Europe in the coming years.

Although it has traditionally been considered an endemic disease in tropical and subtropical regions, recent evidence suggests that climate change is favoring an alarming increase in its incidence and geographical spread, which has brought the threat of leishmaniasis to the doors of Europe. .

Risk of West Nile virus outbreaks increases five-fold

Along the same lines, the increase in cases of West Nile fever is worrying. In 2023, the number of human cases of locally acquired West Nile virus in Europe exceeded 800, including 69 deaths. On the European continent, the pathogen has become endemoepidemic with a large increase in the intensity, frequency and geographical expansion of outbreaks, since high temperatures, induced by climate change, accelerate the capacity of the virus vectors, such as mosquitoes of the genus Culex.

In the coming decades, the risk of outbreaks caused by West Nile virus is expected to increase by up to five-fold, the proportion of European land areas affected will double, and between 161 and 244 million people will be at risk of contracting the disease.

On the other hand, the increase in sea surface temperatures has led to a greater percentage of the European coast next to brackish waters becoming ecologically suitable for pathogenic bacteria of the genus Vibrio. This bacterial genus contains more than 100 confirmed species, twelve of which have been shown to cause infections in humans.

In aquatic environments, Vibrio bacteria tend to be more common in warmer waters, especially above 17°C, and are particularly sensitive to changing environmental conditions, so associated infections will increase due to global warming.

The thing doesn’t end there. In its latest World Malaria Report, published in November 2023, the World Health Organization warned that climate change had the potential to undermine progress in the global fight against the disease and may facilitate its spread in temperate areas such as Europe and the United States of America. Of course, climate change alters the conditions of pathogens and vectors of zoonotic diseases.

Unfortunately, climate impacts often affect those least able to respond, leaving the poorest among the most vulnerable. People with existing health problems, such as cardiovascular disease or diabetes, are also more fragile in a more extreme environment.

Climate change is a present and deadly scenario, which alters the conditions of pathogens and vectors of zoonotic diseases, with room to worsen and affect the well-being of billions of people. That is why it is crucial to establish a responsible and global commitment that accelerates climate action and mitigates future misfortunes.

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