What are drug-resistant infections?

Our collective overuse and misuse of antibiotics is causing one of the most urgent global health problems: drug-resistant infections. But what are drug-resistant infections, who is affected by them, and what can we do to prevent their rise and spread? 

Illustration of an arrow in a circle with four quadrants, each filled icons of: a building, a bird, a plant and the globe.
Our collective overuse of antibiotics in humans, animals and plants is accelerating the development and spread of drug-resistant infections.
Credit: Ryan Chapman/Wellcome
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What are drug-resistant infections?
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What are drug-resistant infections? 

Infections become drug-resistant when the microbes that cause them adapt and change over time, developing the ability to resist the drugs designed to kill them. 

One of the most common types of drug resistance is antibiotic resistance. In this process bacteria – not humans or animals – become resistant to antibiotics. These bacteria are sometimes called ‘superbugs’

The result is that many drugs, such as antibiotics, are becoming less effective at treating illnesses. Our overuse of antibiotics in humans, animals and plants is speeding up this process. 

Without antibiotics that work, routine medical procedures like hip replacement surgery, common illnesses like diarrhoea, and minor injuries could become life-threatening. 

Why are drug-resistant infections dangerous?  

Drugs like antibiotics are a vital tool for modern medicine, used to prevent and treat infections. As drug-resistant infections have become more common, modern medicine as we know it is at risk. 

Without effective antibiotics, common infections that were once easily treatable – such as gonorrhoea and urinary tract infections – are becoming untreatable or need lengthy hospital stays. 

Routine medical interventions, such as chemotherapy, organ transplants and other surgeries, are becoming less safe because of the infection risk. 

Childbirth is also becoming riskier without effective antibiotics to control infections around the time of birth. Every year, over 200,000 newborn babies, mostly in low- and middle-income countries, die because of sepsis that is resistant to antibiotics

Other drugs are also at risk of becoming less effective due to resistance, including antifungals, antivirals and antimalarials. This makes it harder to treat fungal infections, HIV or malaria, for example.

Who is affected by drug-resistant infections?  

Drug-resistant infections can affect anyone, anywhere. We are all at risk of infections from drug-resistant bacteria. 

Researchers estimate that over 1.27 million people died from antibiotic-resistant bacterial infections in 2019. This is around 3,500 people on average every day in more than 200 countries and territories.  

Tuberculosis (TB) continues to be one of the most dangerous infectious diseases in the world, and multidrug-resistant tuberculosis is on the rise. 

Out of the 10.6 million people diagnosed with tuberculosis globally in 2022, around 410,000 cases were caused by multidrug-resistant strains. And about only two in five people with drug resistant tuberculosis accessed treatment.

This poses new risks, especially for children who are much more vulnerable to the disease, and is a major public health risk.  

While recent reports and data give us a clearer picture, understanding the true health burden of drug-resistant infections is challenging because of lack of data and standardised surveillance across different regions and countries. It is possible that many more people are affected than we realise. 

How does drug resistance happen?  

Like all living things, microbes evolve over time in response to their surroundings. Antibiotic resistance is an example of this evolution, occurring when bacteria change in a way that makes antibiotic substances harmless to them.  

They do this in several ways. Some bacteria can ‘neutralise’ the antibiotic before it can do harm. Others have learned to quickly pump the antibiotic out of their cells. And others can change their outer structure so the antibiotic cannot attach to the bacteria and kill them.   

The resistant bacteria survive and multiply. If they are passed on to other people, animals or the environment, resistant infections can spread rapidly.  

For example, it took only five years for an antibiotic resistant strain of K. pneumoniae to spread globally from the USA, where it was first found in 2003, to Israel in 2005 and then to Italy, Colombia, the United Kingdom and Sweden by 2008.

Why are we seeing more drug-resistant infections?  

Drug resistance is a natural phenomenon, but its recent growth is largely driven by human activity. Unnecessarily exposing bacteria to medicines creates more opportunities for drug resistance to develop and spread. Globally, the World Health Organization estimates that only half of antibiotics are used correctly [PDF 3.9MB]. 

Antibiotics are used in huge quantities in livestock, fish and crop farming to promote growth and prevent diseases. Over 70 percent of all antimicrobials sold are used in animal farming. And this number is on the rise – with current projections estimating an 8 per cent increase in antimicrobial use in farming by 2030

Antibiotics are also widely misused in human healthcare. Of the 150 million prescriptions for antibiotics written by doctors in the USA every year, it’s estimated 50 million were not necessary [PDF 3.9MB].  

In some countries, regulation on antibiotic use is poorly enforced or doesn’t exist at all. People can buy antibiotics over the counter, and antibiotics can be mistaken for other medications such as painkillers, leading to their overuse and misuse.  

Although there is an urgent need to limit the inappropriate use of antibiotics, currently more lives are lost because of lack of access to life-saving antibiotics. Using antibiotics appropriately – and making them available and affordable where they’re needed – are both important for improving global health. 

When will drug-resistant infections be a problem?  

Drug-resistant infections are already a problem.  

If we don’t act now, it’s projected that 10 million people could die each year from drug-resistant infections by 2050.  

That’s means more people could die from drug-resistant infections than cancer. And six times more deaths than diarrhoeal diseases, measles and cholera combined.  

All countries are – and will be increasingly – affected. But the greatest health burden will be in low- and middle-income countries where health systems are not as strong.

Are drug-resistant infections a global problem?  

Yes. In an era of increased mobility and globalisation, microbes cannot be contained within national borders, spreading between people, animals and through environmental channels like water or soil.  

Across the world drug resistance is very common. In 2019, close to one in five bacterial infections in OECD countries were resistant to antibiotics.

In low- and middle-income countries, resistance is even higher, with resistance rates as high as 80 to 90 percent in some places [PDF 968KB].  

And genes associated with drug-resistant bacteria have even been found in the Arctic Circle and Antarctica, some of the remotest places on earth. 

Drug-resistant infections are also a threat to global economies and healthcare systems. The World Bank estimates that drug-resistant infections have the potential to cause a level of economic damage like that caused by the 2008 financial crisis.  

Can we stop drug-resistant infections?  

We can’t completely stop drug-resistant infections from happening but, by taking action now, we can slow them down. 

Drug resistance is a natural evolutionary process. Resistance to antibiotics was recorded even before the first clinical use of penicillin in the 1940s. Since then, resistance to all classes of antibiotics has been discovered. 

Although we can’t stop it, we can control the pace of resistance development and spread – for example, through better use of existing antibiotics and the development of new ones.

How can we slow down drug-resistant infections?  

As a global problem, drug-resistant infections need a coordinated, worldwide response.  

Better use of existing antibiotics across human healthcare and the animal sector is vital. With limited exposure to antibiotics, bacteria will have fewer opportunities to develop resistance. 

Healthcare communities around the world are making concrete efforts in this area. 

Alongside ‘antibiotic stewardship’, we need robust surveillance in all countries and across sectors to better understand the presence and spread of resistance and take actions where and when they are needed.  

But if we are to really slow resistance, we need to create a more equitable and sustainable ecosystem of research and development for infectious disease.

This includes developing low-cost and fast diagnostics, creating new antibiotics, and ensuring equitable access to life-saving treatments. 

Preventing infections is another route for curbing drug resistance. Developing new vaccines, access to clean water, better sanitation and hygiene are effective ways of doing that. 

What is the difference between antibiotic resistance, antimicrobial resistance and drug-resistant infections?  

Antibiotic resistance is the ability of bacteria to change in a way that makes antibiotics ineffective.  

Antimicrobial resistance (AMR) is a broader term, which includes antibiotic resistance and other types of drug resistance developed by viruses (such as HIV), fungi (such as Candida) and other microbes.  

Drug-resistant infections is a term we use to describe illnesses that have been caused by resistant microbes, resulting in an infection that is much harder – or potentially impossible – to treat. 

Wellcome's report Reframing Resistance recommends drug-resistant infections as the term that is most easily understood when communicating with the public. 

We’re funding research to better understand what causes and drives infectious diseases to escalate and the solutions to control their impact. Explore our current funding call:

Infectious Disease Award: Understanding dengue and Zika spread, immunity and clinical outcomes

This article was first published on 27 January 2021.