By 2050, nearly 40 million people could die from infections caused by antibiotic-resistant superbugs, a new study estimates

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The number of deaths worldwide due to infections resistant to the drugs used to treat them could increase by almost 70 percent by 2050, according to a new study, highlighting the burden of the ongoing superbug crisis.

In total, there could be more than 39 million deaths worldwide between 2025 and 2050 that are directly attributable to antimicrobial resistance, or AMR, according to the study, published on Monday in the journal The Lancet.

Antimicrobial resistance occurs when pathogens such as bacteria and fungi develop the ability to evade the drugs designed to kill them.

The World Health Organization has described AMR as “one of the greatest global threats to public health and development.” It is caused by the misuse and overuse of antimicrobial drugs in humans, animals and plants, which can lead to pathogens developing resistance to these drugs.

The new study shows that “we expect to see worsening” in the prevalence of AMR and its impact, said lead author Dr. Chris Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington.

“We need to pay appropriate attention to new antibiotics and the responsible use of antibiotics so that we can address this really quite big problem,” he said.

The researchers – from the Global Research on Antimicrobial Resistance Project, the Institute for Health Metrics and Evaluation and other institutions – estimated deaths and illnesses attributable to or associated with antimicrobial resistance for 22 pathogens, 84 pathogen-drug combinations and 11 infections in 204 countries and territories from 1990 to 2021. One death attributable to antimicrobial resistance was directly caused by it, while one death associated with AMR may have another cause that was exacerbated by antimicrobial resistance.

The data used for these estimates included approximately 520 million individual records.

The researchers found that between 1990 and 2021, deaths from AMR fell by more than 50% among children under five, but increased by more than 80% among adults aged 70 and over – a trend that is expected to continue.

It was surprising to see these patterns emerge, Murray said.

“There have been two opposing trends: a decline in deaths from AMR under 15, largely due to vaccination, water and sanitation programs, some treatment programs and the success of those programs,” Murray said.

“At the same time, the number of deaths among those over 50 is steadily increasing,” he said, as the world is aging and older people are more vulnerable to serious infections.

The researchers found that the pathogen-drug combination that caused the largest increase in burden across all age groups was methicillin-resistant Staphylococcus aureus, or MRSA. For this combination — the antibiotic methicillin and the bacteria S. aureus — the number of deaths attributable to this combination has nearly doubled, from 57,200 in 1990 to 130,000 in 2021.

Using statistical models, the researchers also produced estimates of deaths and illnesses attributable to AMR by 2050 under three scenarios: if the current climate continues, if new effective antibiotics are developed to combat resistant pathogens, and if the quality of medical care for infections improves worldwide and access to antibiotics is better.

The number of deaths from antimicrobial resistance is projected to increase by 2050 unless action is taken to improve access to high-quality healthcare, effective antibiotics and other means to control and treat infections.

The researchers estimated that by 2050, the number of deaths due to antimicrobial resistance could reach 1.9 million worldwide, and the number of deaths related to antimicrobial resistance could reach 8.2 million.

According to the data, South Asia, Latin America and the Caribbean, and sub-Saharan Africa are the regions most affected by AMR and deaths from it. And in many of these regions, there is no equitable access to quality health care, Murray said.

“Unfortunately, there are still a lot of places in poor areas where people who need antibiotics just don't get them, and that's a big part of it. But it's not just about the antibiotics. It's about when you're sick, whether it's a child or an adult, and you're sent to the hospital and you're essentially given a treatment package that includes things like oxygen,” Murray said.

“In resource-poor settings, even basic things like oxygen are often not available. And then if you're very sick and need intensive care, there are large parts of the resource-poor world – most of it, actually – where you don't have access to that kind of care,” he said. “So there's a spectrum of supportive care as well as antibiotics that really make a difference.”

In a scenario where the world has better healthcare, a total of 92 million deaths could be prevented between 2025 and 2050, the researchers predict. And in a scenario where the world has new, more effective medicines, a total of about 11 million deaths could be avoided.

The “innovative and collaborative” approach of this study provides a “comprehensive assessment” of antimicrobial resistance and its potential burden on the world, wrote Samuel Kariuki of the Kenya Medical Research Institute in a commentary on the new study in the Lancet.

However, he warned that the forecast models do not take into account the emergence of new superbugs “and could lead to an underestimation if new pathogens emerge.”

Overall, “these data should lead to investments and targeted actions” to address the growing challenge of antimicrobial resistance in all regions of the world, Kariuki wrote.

The new paper is the culmination of decades of research on the global burden of antimicrobial resistance, said Dr. Steffanie Strathdee, associate dean for global health sciences and distinguished professor at the University of California San Diego School of Medicine, who was not involved in the study.

Strathdee experienced the health impact of antimicrobial resistance firsthand when her husband nearly died from an infection with a superbug.

“I have been living with antimicrobial resistance affecting my family for eight years. My husband almost died from an infection with a superbug. It's actually one of the infections highlighted in this article,” said Strathdee, who serves as co-director of the Center for Innovative Phage Applications and Therapeutics at UC San Diego.

While on a Thanksgiving cruise on the Nile in 2015, Strathdee's husband, Tom Patterson, suddenly began to experience severe stomach cramps. When a clinic in Egypt failed to relieve his worsening symptoms, Patterson was flown to Germany, where doctors discovered a grapefruit-sized abdominal abscess filled with Acinetobacter baumannii, a virulent bacteria resistant to almost all antibiotics.

The annual number of people dying from Gram-negative bacteria such as A. baumannii that are resistant to carbapenems – a class of last-resort antibiotics used to treat serious bacterial infections – increased by 89,200 between 1990 and 2021, more than any other class of antibiotic during that period, according to the new study.

“This is one of the most pressing pathogens, which is one of these gram-negative bacteria,” Strathdee said. “And when my husband got it, he was 69. So he's exactly the age that's highlighted in this article, which is that older people are going to be more affected by this in the future because our population is aging and people have comorbidities, like diabetes, like my husband.”

Strathdee's husband recovered after treatment with phages, viruses that specifically attack and kill bacteria and can be used as a treatment for antimicrobial-resistant bacterial infections.

“The main alternative to antibiotics is phage therapy, or bacteriophage therapy, and it saved my husband's life,” Strathdee said. “Phages can be used very effectively in conjunction with antibiotics to reduce the amount of antibiotics needed, and they may even have potential for use in livestock and agriculture.”

The new study gives Strathdee hope that the world can reduce the potential burden of antimicrobial resistance. This will require improving access to antibiotics and newer antimicrobial drugs, vaccines, clean water and other aspects of quality health care worldwide, she said. At the same time, antibiotic use in livestock farming, food production and the environment must be reduced, as this can lead to more resistance.

“There may be hope on the horizon,” Strathdee said. “If we scaled up these interventions, we could dramatically reduce the number of deaths in the future.”