Across the globe, zoonotic and vector-borne diseases (ZVBDs), illnesses that jump from animals to humans, either through direct contact or via carriers such as mosquitoes, have increased significantly over the past few decades, claiming millions of lives each year. Now, the spotlight for this is on the Amazon rainforest.
Amazon rainforest: infectious diseases surging
An estimated 75% of all newly emerging infectious diseases, along with more than 60% of all human pathogens, are spread from animals.
Mosquito-borne diseases alone put more than 80% of the global population at risk. Their spread threatens not only public health, but also the world economy.
Even before coronavirus shut down, economies and filled hospitals, emerging infectious diseases were costing the world over $1tn a year. The pandemic made those costs painfully visible, but did not create the problem, it exposed it.
Since 2003, outbreaks and pandemics have taken more than 15 million lives and drained approximately $4tn from the global economy.
A study published in One Earth, a sustainability journal from Cell Press, warns that this crisis is no accident. Deforestation, the climate crisis, and environmental degradation are creating the perfect storm for pathogens to thrive and spread.
The lead author of the study, Raquel L. Carvalho, warns about the risks in Europe associated with vector-borne diseases:
Europe is increasingly becoming a favourable environment for mosquito-borne diseases, as prolonged summers, elevated temperatures, and heavier rainfall create conditions in which mosquito populations can establish and spread in regions where they had previously been unable to survive.
Deforestation driving the emergence of the next pandemic
Since the 1940s, changes in how humans use land, cutting down forests, expanding agribusiness, and pushing deeper into wild areas, have been linked to more than one-third of all new infectious diseases.
The climate crisis is creating conditions where mosquitoes, ticks, and pathogens flourish. Rising temperatures extend mosquito breeding seasons and allow disease-carrying insects to spread into places where winters once kept them at bay.
Meanwhile, deforestation and land-use changes bring humans into closer contact with wild animals, increasing the odds of a spillover event. Poverty and weak healthcare systems magnify the danger, turning exposure into tragedy.
According to a study published in the International Journal of Emergency Medicine, climate change is also disrupting food production and supply, creating conditions that allow harmful microbes and toxins to thrive, while extreme weather and rising temperatures increase the risk of foodborne illnesses, such as Salmonella and E. coli.
Diseases, viruses, bacteria: out of control
Recently, we’ve seen a sharp increase in the spread of diseases caused by parasites, viruses and bacteria, including dengue, Zika, chikungunya, oropouche, malaria, Lyme disease, among others.
The spread of oropouche fever, transmitted by the tiny culicoides paraensis mosquito, popularly called maruim, is another alarming sign.
According to the Pan American Health Organisation (PAHO), in 2025, 12,786 confirmed oropouche cases were reported in the Americas region, including over 11,888 cases in Brazil.
In Brazil, oropouche outbreaks originated in the AMACRO region (a deforestation hotspot named after the states of Amazonas, Acre, and Rondônia) and have already spread across the country to the state of Espírito Santo, with 6,322 recorded cases in 2025, and across the world.
The Amazon rainforest is considered one of the world’s largest reservoirs of zoonotic diseases. Many scientists have repeatedly cautioned that environmental disruptions are driving the rise of infectious diseases and have highlighted the imminent risk of a lethal pathogen originating from the region.
Joel Henrique Ellwanger, biologist and researcher at the department of genetics at the Federal University of Rio Grande do Sul (UFRGS), said:
Climate change will trigger important ecological changes in the Amazon, many of them with the potential to reduce its biodiversity, facilitating the spread of known disease vectors and increasing the chances of new diseases emerging.
Putting communities at risk
A study, conducted by Raquel L. Carvalho, professor at the University of São Paulo (USP), and her team, analysed 312 papers that addressed 39 different diseases in 79 countries. Much of this work focuses on the pathogens themselves or the insects and animals that transmit them. In contrast, far fewer studies consider who’s exposed or why some groups are more vulnerable once exposed.
Carvalho highlighted gaps in existing research:
Only 7.4% of the studies looked at the full picture: hazard, exposure, and vulnerability. Studying where mosquitoes live might show potential danger, but it doesn’t reveal who is most at risk, or why certain communities are more likely to fall ill.
Diseases like dengue fever, the West Nile virus, and leptospirosis thrive not only because mosquitoes and rodents are abundant, but also because people live in poor housing without proper sanitation, or because climate change drives mosquitoes into new regions.
If these human and environmental factors are ignored, predictions of where and when outbreaks will happen will always likely fail.
Most studies carried out come from the United States, China, and Europe, while tropical regions, where the risks of diseases are greatest, remain under-studied. Brazil and Kenya stand out as exceptions, but vast regions of Africa, South America, and Asia are left with little attention.
The places most likely to produce the next pandemic are also the least prepared to prevent it.
Building a better response
The researchers of the study explained that prevention requires a more complete picture of the risks, meaning the combination of ecological data with human and social realities.
Poverty, education, housing, and access to healthcare are as important as climate change and land use.
For example, in East Africa, malaria was mapped out more effectively when researchers combined mosquito data with measures of poverty and healthcare. In New York, Lyme disease predictions improved when scientists considered both tick abundance and human behaviour. Understanding hazard, exposure, and vulnerability together gives us tools for prevention.
Carvalho pointed out that tackling the threat won’t be easy, but insists that stronger monitoring and international cooperation are key:
It’s clear that there’s no obvious solution, but stronger surveillance systems, especially in disease hotspots, can act as an early-warning radar.
Cross-border scientific cooperation can ensure that no region is left behind. Additionally, a One Health approach, recognising that human, animal, and environmental health are interconnected, must guide every decision.
Communities living in poverty, the ones closest to the frontlines of environmental change, are the first to suffer. If we continue to ignore the full complexity of disease risk, we condemn these vulnerable populations to pay a high cost, while leaving the rest of the world exposed.
The coronavirus pandemic taught us a lesson, showed us the cost of being unprepared. The next pandemic could be much worse, driven by climate extremes and ecological disruption.
The line between environmental neglect and human suffering is very thin. It shouldn’t be hard to understand that our health depends on the health of our planet, one protects the other.
Feature image via ABC News/Youtube.
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