Antimicrobial Resistance Is Killing Millions. Climate Change Is Making It Worse.

Born with cystic fibrosis, Ella Balasa is used to doing several breathing treatments a day and taking antibiotics to fight the infections in her lungs. By her mid-twenties, the antibiotic courses were taking longer and longer to work. In 2019, she got severely sick. Despite a combination of oral and intravenous antibiotics, her lungs would fill up with mucus every few hours. Her lung function dipped down to the teens. (Normal function is 80% or higher.) “I’m not going to live to be able to fight off these infections,” she remembers thinking. “Antibiotics aren’t working, and that’s all we have, so I don’t know what I’m going to do.” In her mid-twenties, Ella Balasa faced a serious lung infection caused by Pseudomonas aeruginosa, a bacterium that left her struggling to breathe. Credit: Laventie Benoit-Joseph/Flickr, CC BY-NC-ND 2.0 “Antimicrobial use remains one of the central drivers of AMR, but climate change can modify the environmental, ecological, and social conditions that allow resistant microorganisms and resistance genes to emerge, persist, move, and reach humans, animals, and ecosystems.” According to the World Health Organization (WHO), one in six infections is drug resistant. In some areas, it’s one in three. In 2021, WHO estimated that bacterial antimicrobial resistance (AMR) was associated with more than 4.7 million deaths around the world. There are many factors driving the rise of AMR, including the misuse and overprescription of antibiotics not just for humans, but for controlling disease among livestock and agricultural crops. But a growing body of research suggests there’s another piece of the puzzle: a changing climate. “Antimicrobial use remains one of the central drivers of AMR, but climate change can modify the environmental, ecological, and social conditions that allow resistant microorganisms and resistance genes to emerge, persist, move, and reach humans, animals, and ecosystems,” Ronan Adler Tavella, an environmental health scientist at the Antimicrobial Resistance Institute at the Federal University of São Paulo, told Eos in an email. How Do Antimicrobial-Resistant Genes Spread? Antimicrobial-resistant genes (ARGs) are found in nature because different microbial groups are often locked in ecological competition. In the soil, water, and even air, microbes produce antimicrobial compounds and resistance mechanisms designed to take out or communicate with competitor microbes. Bacteria are also capable of a unique phenomenon called horizontal gene transfer, meaning that bacteria can transfer genes between each other outside of a parent-offspring relationship, even across species. Soil microbes, seen here under a microscope, naturally produce antibiotic genes as a form of offense against other microbes—and antibiotic-resistant genes as a form of defense. Credit: Courtesy of Pacific Northwest National Laboratory/Flickr, CC BY-NC-SA 2.0 The field of medicine was transformed when physicians and researchers began taking advantage of ARGs to treat disease in the early 20th century. The broad class of antimicrobial drugs is designed to kill, inactivate, or slow the growth of microbes, which can include bacteria as well as viruses, parasites, and fungi. “Antibiotics themselves are the pillar of basic and modern medicine.” Antimicrobials are used to treat animal bites, pneumonia, strep throat, urinary tract infections, Lyme disease, cardiac infections, diarrhea, sexually transmitted diseases, ringworm, malaria, yeast infections, valley fever, eye and ear infections, parasitic infections, and many, many other ailments. In fact, experts say there’s not much we can do without them. “Antibiotics themselves are the pillar of basic and modern medicine,” said Sarah Paulin-Deschenaux, a microbiologist and technical officer on antimicrobial resistance in WHO’s AMR department. “We need to have effective antibiotics to enable the treatment of simple cuts, the allowance of surgical procedures, [and] safe delivery for cancer chemotherapy.” But there’s a catch. An antimicrobial designed to kill a specific microbe—say, E. coli—doesn’t kill every single microbe. It kills many of them, but the most resistant ones survive. These microbes with ARGs can reproduce, creating a whole new community of microbes that don’t respond to the antimicrobial, creating the need for another. However, overuse of antibiotics isn’t the only thing that can lead harmful microbes to grow stronger and spread. Everything from heavy metals to fertilizers to pharmaceutical waste in soil can cause stress to soil microbes. “Anything that stresses them—heat, chemicals—all this is going to increase their mutation rates,” said Jason Burnham, an infectious disease and medicine professor at Washington University and VA St. Louis. Fighting Infection in a Climate Hot Spot Because Balasa, the cystic fibrosis patient, had to take antibiotics so often, the microbes in her body, which tend to proliferate in the scar tissue of her lungs, grew resistant over time. But some antibiotic-resistant infections come seemingly without warning. Shortly after finishing her master’s degree in Mumbai, India, Bhakti Chavan was diagnosed with drug-resistant tuberculosis (TB), though she had no previous history of the disease. For 8 months, Chavan received antibiotic injections six times a week. Her course of oral antibiotics, a combination of four to five drugs taken daily, went on for another 16 months. Her side effects included depression, a darkened skin tone, and heavy nausea. She was unable to work for about 2 years. She stopped seeing friends and even stopped looking in the mirror. “Without having any previous history of TB, I got directly diagnosed with drug-resistant tuberculosis,” she said. “That means the strains are already circulating in the environment.” Mycobacterium tuberculosis is the bacterium that causes tuberculosis. Shortly after college graduation, Bhakti Chavan was diagnosed with a drug-resistant form of tuberculosis, despite having no history of the disease. Credit: Ajay Kumar Chaurasiya/Wikimedia Commons, CC BY-SA 4.0 India is a hot spot for both high heat and AMR, which can be a deadly combination. As of 2021, an estimated 31% of India’s population over the age of 15 had a tuberculosis infection. It’s a situation Chavan is all too aware of. Humans are struggling in the face of climate change, but microbes “are growing faster, they are becoming stronger, and they are becoming resistant,” Chavan said. “We need to seriously look into climate change right now. Because we need to be one step ahead of them.” Strength in Adaptability The climate has changed rapidly in the decades since the Industrial Revolution, leaving many individuals, communities, and nations struggling to adapt. In contrast, adaptability may just be bacteria’s greatest strength, Burnham explained. For “some bacteria, their doubling time, or their ability to make a copy of themselves, is like 20 minutes. So, they can change really quickly to anything in their environment, whether that’s heat or pollutants or antibiotics,” Burnham said. “Obviously, we humans can’t do that as fast.” Higher temperatures are making it easier for mosquitoes carrying diseases like malaria, seen here under a microscope, to thrive. Credit: Hanna Sörensson/Flickr, CC BY-SA 2.0 Burnham used the example of the sickle cell anemia gene. Over time, the gene variant developed in people who live in tropical, mosquito-friendly areas where malaria is endemic because having a copy of the gene provides a strong resistance to malaria. There were “similar conditions for so long that humans actually were able to adapt,” Burnham said. “Now things are changing so fast that they can’t” evolve quickly enough. Higher temperatures are linked to increased risk of tuberculosis, COVID-19, and a wide array of other infectious diseases. “Almost every type of bacterial infection categorization that we have, those are increased in warmer, more humid times of the year,” Burnham said. “So, surgical site infections, urinary tract infections, skin infections, pneumonias, bloodstream infections. All of these things are more common when it’s warm.” All of this represents an indirect, but real, link between climate change and AMR: When it’s hotter, more people are sick. And when more people are sick, more people are taking antibiotics. Paulin-Deschenaux of WHO was careful to state that climate change is not the cause of AMR but noted that evidence linking the two is growing. There is some evidence indicating that climate change may “accelerate the development and spread of drug-resistant infections,” she said. As a cystic fibrosis patient, Ella Balasa has battled forms of antimicrobial resistance throughout her life. Credit: Ella Balasa Balasa, the cystic fibrosis patient, now works as a patient advocate and consultant, a role in which she speaks about the importance of examining alternatives to antibiotics. She herself has found success with an experimental bacteriophage treatment. Bacteriophages are viruses that infect and destroy bacteria. “Even if we develop new antibiotics in the future, bacteria are going to become resistant no matter what,” Balasa said. “And so, I really urge researchers and drug developers to think outside the box of the development of more traditional antibiotics. I just don’t think traditional antibiotics are a viable long-term solution.” Another important piece of the puzzle, Paulin-Deschenaux emphasized, is prevention of infections in the first place, particularly in areas without strong health care systems and infrastructure. “One of the best lines, really, for mitigating AMR is strengthening prevention: investing in clean water, sanitation, hygiene, and infection prevention practices, as well as immunization.” The Air We Breathe There’s more to the story than adaptability. A changing climate can also enhance bacteria’s ability to travel from one area of the globe to another. AMR can spread through wastewater, such as when patients taking antibiotics pass remnants of the drugs as waste. When a natural disaster, such as a hurricane or flood, affects wastewater treatment plants, the spread can be dramatically sped up. Some research has even indicated that as glaciers melt, ARGs stored in the ice for thousands of years can be released into the environment. AMR’s pathways through the soil can be affected by climate too. For instance, drought conditions can lead to desiccated soils that in turn lead to an escalation in the production of both antibiotics and ARGs. But perhaps the most understudied transmission pathway is the air itself. Airborne bacteria are shown here, magnified 3,000 times by optical microscopy. Credit: Josef Reischig/Wikimedia Commons, CC BY SA 3.0 Drug-resistant pathogens can travel vast distances when they are aerosolized, or made small and light enough to be carried through the air: A 2024 study showed that aerosolized bacteria and fungi (including resistant species) can travel thousands of kilometers through the air. But it’s “very, very hard to analyze the air microbiome,” in part because of the potential for contamination, said Fumito Maruyama, an environmental microbiologist at Hiroshima University who focuses on antibiotic resistance and pathogens in the natural environment. “That’s one reason why we still don’t know much about the air resistome.” Maruyama and Salametu Saibu, an environmental microbiologist and postdoctoral researcher in his lab, introduced the concept of the “air resistome,” or the community of ARGs held in and traveling through the atmosphere, in a 2026 review paper. Organisms carrying ARGs can enter the air via soil or water, then be redeposited in soil or water in a new location, Saibu explained. These particles can be inhaled by humans, potentially exposing them to antibiotic-resistant microorganisms or ARGs. Increased air temperatures also make it easier for bacteria to horizontally transfer genes, she added. Here, E. coli is seen during the process of bacterial conjugation, a form of horizontal gene transfer. The thin appendages labeled “F-pilus” are conduits the microbes use to share DNA. Credit: Jonasz Patkowski/Wikimedia Commons, CC BY-SA 4.0 “When the temperature is warm, it enables transmission of antibiotic-resistant genes from one community to another community, from one bacterial population to another bacterial population,” Saibu said. “There’s no barrier, no barrier at all.” But climate change is more than just higher temperatures. Cascading effects can lead to increased risk of disasters such as flooding, drought, and wildfires. Wildfires can worsen respiratory conditions, leading to increased hospital visits and antibiotic use. A less studied link between wildfire smoke and AMR, Adler Tavella explained, is smoke’s potential ability to aerosolize resistant microbes and genes. “Wildfire smoke should not be viewed only as chemical air pollution,” he said. “Fires can aerosolize microorganisms from soils, vegetation, and burned biomass, and smoke plumes can transport bacteria, fungi, spores, and other biological particles.” Breathing is, of course, unavoidable, and taking stronger antibiotics to combat increasingly resistant bacteria contributes to a vicious cycle. Though antibiotics can pay off for shorter-term illnesses like Chavan’s bout of drug-resistant tuberculosis, AMR can leave patients with chronic illnesses, like Balasa, with few options. Though the bacteriophage treatment she began in 2020 has been beneficial, in the past few years, she’s been getting sick more frequently again. “You can’t fully get rid of resistant pathogenic bacteria, at least not in the cystic fibrosis lung microbiome. They can’t be eradicated, and they are incessant and very resilient,” she said. Drug-resistant pathogens can travel vast distances when aerosolized. This satellite video shows aerosols visible from NASA’s Goddard Earth Observing System model. Blue represents sea salt aerosols, pink is dust aerosols, orange/red is smoke from fires, and green is sulfates from pollution and volcanoes. Credit: NASA’s Global Modeling Assimilation Office (GMAO) and NASA’s Scientific Visualization Studio (SVS) The One Health Approach With a wealth of studies documenting the inequitable effects of climate change, it may come as no surprise that the highest number of drug-resistant infections occur in low- and middle-income countries, where health systems are the weakest. It’s another example of a dangerous feedback loop: With infections more common and high-quality diagnostics less common, people in these countries are more likely to get sick and less likely to receive the appropriate treatment. “It’s a global issue, and we need to fight it together.” A lack of treatment access, inappropriate or unregulated use of antimicrobials, and a dearth of resources that could prevent infection, such as clean water and immunization programs, make for a dangerous combination, said Paulin-Deschenaux. “That coming all together really is a melting pot for antimicrobial resistance.” Researchers are largely united in viewing AMR as a problem requiring a multidisciplinary, global effort, or what WHO often calls a “One Health” approach. The approach recognizes that the health of humans, animals, plants, and the wider environment are linked. Therefore, the prevention, detection, and treatment of disease require collaboration between scientists, physicians, public health specialists, governments, industry, and even patients. “Everybody must be informed about antibiotic resistance and about the environment, how we should take care of the environment for the next generation to come,” Saibu said. “It’s a global issue, and we need to fight it together.”‘ Across the globe, geoscientists are stepping up to the challenge. In China, soil scientists are comparing soil resistomes across the country to learn more about how agricultural practices are contributing to AMR’s spread, while environmental engineers are developing methods to degrade antibiotic contaminants in water and slow their transport through soil. In the United States, environmental scientists are studying the presence of ARGs in urban karst aquifer systems and how different soil management strategies affect the resistome. In Brazil, environmental scientists like Adler Tavella are investigating the links between catastrophic floods and AMR, while others are researching the use of bacteriophages as antibiotic alternatives. In South Africa, researchers are studying the role of extracellular DNA in transporting ARGs from wastewater treatment plants to rivers. In May 2026, WHO adopted an updated global action plan on antimicrobial resistance that outlined priorities, including raising awareness, enhancing surveillance systems and laboratory networks, improving infection prevention to reduce the need for antimicrobials, ensuring equitable access to and appropriate use of the drugs, and accelerating research into AMR. The report notes the growing importance of tackling the problem, suggesting that AMR could reduce global life expectancy by 1.8 years within a decade and cause up to 39 million deaths by 2050. “Solving AMR will require much broader collaboration than we traditionally imagine,” said Lianping Yang, a public health scientist at Sun Yat-sen University who researches AMR and climate change. “If we want to protect antibiotics for future generations, we need to think beyond prescribing practices. We need a healthy environment, a healthy planet, a stronger health system, and better preparation for a changing climate.” Moreover, Yang said, “sustainable development strategies are important for helping the global, especially the low- and middle-income countries to address the dual threats of climate change and AMR.” —Emily Gardner (@emfurd.bsky.social), Deputy Editor Citation: Gardner, E. (2026), Antimicrobial resistance is killing millions. Climate change is making it worse., Eos, 107, https://doi.org/10.1029/2026EO260274. Published on 1 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.