Climate change and antimicrobial resistance – when drugs designed to kill microbes become ineffective – are two major global health crises. But did you know that the two challenges are connected?
As the climate crisis worsens, millions of people around the world are experiencing the health consequences of extreme weather and climate events such as droughts, floods and heatwaves.
One of the lesser-known consequences is the increased prevalence and spread of bacterial, viral, parasitic and fungal diseases in humans, animals and plants – as well as the likelihood that pathogens that cause diseases will evolve and become resistant to medicines.
This leads to the rise and spread of drug-resistant infections that are difficult or potentially impossible to treat with antimicrobial medicines, including antibiotics, antivirals, antifungals and antiparasitics, and puts modern medicine at risk.
For example, common bacterial infections, infections after childbirth or surgery, fungal infections, HIV and malaria, could become harder to treat and increasingly fatal. Millions more lives could be lost each year.
The climate crisis worsens the threat of antimicrobial resistance in several ways. Temperature is intimately linked with bacterial processes and infections.
As temperatures warm with climate change, bacterial infection rates may increase and diseases can spread to higher altitudes and latitudes where they were not previously found. Bacteria can also grow and reproduce faster and swap genes with one another (a process called horizontal gene transfer). The faster this occurs, the more likely bacteria are to develop antibiotic resistance.
Higher temperatures may also cause drought, which results in water shortages and a lack of food. This can cause malnutrition, with children most vulnerable, lowering immunity and the ability to fight off infections. Infections can spread quickly in these conditions and could become drug-resistant, with mortality rates likely to increase.
Flooding and drought can lead to displacement, overcrowding and a lack of clean water. Poor sanitation and reduced access to treatment and medicines in disasters like these can cause rises in infections that can become drug-resistant.
These extreme conditions, fuelled by climate change, will also put increasing pressure on farmers and livestock producers. Antibiotics are often used in food production and could further increase to protect diminishing crop and animal yields. The overuse and misuse of antibiotics in farming is increasing the development and spread of drug-resistant infections in humans and animals.
Infections are caused by microbes, such as viruses, bacteria or fungi, which can adapt and evolve in response to their surroundings.
As infection rates increase, attempts to reduce these health threats often result in an increase in the use of antimicrobial drugs, such as antibiotics.
The overuse and improper use of these drugs to treat these infections unnecessarily expose bacteria to these drugs. It gives the bacteria more opportunities to evolve, become resistant to the treatment, survive and spread.
Find out more about antimicrobial resistance and drug-resistant infections
The 2023 Lancet Countdown on Health and Climate Change, supported by Wellcome, reports how our climate has become more suitable for disease transmission.
It finds that climate change, along with urbanisation and human movement, has driven an increase in dengue – a life-threatening viral infection that is transmitted from mosquitos to people. Cases have doubled every decade since 1990 and almost half of the world’s population is now at risk. What’s more, is that, in every future climate scenario of global heating, it’s expected that dengue transmission will continue to increase.
As climate change alters temperatures and weather patterns around the world, the risk of vector-borne diseases like dengue fever and Zika virus will increase. Here’s what that means for global health and what can be done to limit the damage.
The Countdown also reports that Vibrio pathogens, which are found in coastal brackish waters and cause severe wound, ear and gastrointestinal infections, are also expected to increase. The total coastal area that is suitable for Vibrio transmissions has increased by 329km each year since 1982. In 2022, a record 81 countries had coastal areas suitable for Vibrio, with 1.4 billion people living within 100km of these areas and at risk of transmission.
Waterborne diseases like cholera and typhoid are still a leading cause of human morbidity and mortality worldwide. As climate change increasingly impacts global temperatures and weather events, the risk of these infectious diseases will only worsen. But there are actions we can take to reduce these risks.
In one study, researchers developed a database exploring patterns of drug-resistant bacteria in different climates across 41 states in the US. They found that a 10°C increase in daily minimum temperature was associated with small increases in antibiotic resistance for three common pathogens – E. coli, K. pneumoniae and S. aureus.
In another study, researchers looked to the future and estimated that thawing permafrost in the rapidly warming Arctic could unleash antibiotic-resistant strains of bacteria.
As greenhouse gas levels continue to rise and extreme weather and climate events become more frequent, more human and animal populations will be at risk of drug-resistant infections. And, like other impacts of climate change, the challenge of antimicrobial resistance will disproportionately affect low-income countries that are the least responsible for the crisis.
Antimicrobial resistance is already one of the major global health threats of the 21st century. Researchers estimate that 1.27 million people died in 2019 from antibiotic-resistant bacterial infections.
Improving diagnostic tests, collecting better data, improving the way we use existing antimicrobials and developing new classes of antimicrobial drugs can help the world to better prevent, treat and control life-threatening drug-resistant infections. But finding and developing these drugs is challenging:
As the climate crisis threatens to compound the existing threat of drug-resistant infections, the need to progress the discovery of new antimicrobial therapeutics becomes even more urgent.
To minimise the impacts of climate change on antimicrobial resistance, we must work to limit greenhouse gases in the atmosphere and implement solutions that can help people adapt to a changing climate where diseases are widespread.
We also urgently need collective, evidence-based action to control the escalating burden of drug-resistant infections.
Wellcome is supporting research and policy action to better understand the global burden of antimicrobial resistance and accelerate the development of new interventions.
Antimicrobial resistance and climate change are intimately linked, and while some progress is being made to tackle both problems, the scale of these crises requires faster action on a larger scale.
This article was first published on 21 November 2022.
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