Drug-resistant infections: how worried should we be?
Mark Henderson, Head of Communications at Wellcome, explains what drug-resistant infections are and why they are such a pressing issue for all of us.
Infectious diseases are caused by bacteria, viruses, parasites or funguses getting into our bodies. Once inside, they can cause damage directly or by generating a response from our own immune system that causes collateral damage while trying to get rid of the infection. This can lead to anything from a sore throat to septicemia.
Over the past 70 years or so, we have discovered drugs that augment our body's immune response to infections. Antibiotics, for example, kill bacteria, or at least stop them growing – some are general and kill lots of different species of bacteria; others are more specific.
But bacteria are always evolving. An antibiotic targets a particular characteristic of the infectious bacteria, so by specifically killing all bacteria that have this characteristic, any that happen not to have it gain an advantage and are left free to multiply and spread. This creates a population of resistant bacteria that cannot be killed by that antibiotic.
Drugs used to treat infections are called antimicrobials, so this type of drug resistance is also called antimicrobial resistance, or AMR. Antibiotic resistance is the same thing, but specific to antibiotics. However, the term drug-resistant infections makes it clearer that it is the infectious species which is resistant to the drug, not the patient.
Why are drug-resistant infections a problem?
There are already strains of tuberculosis that are resistant to most – even all – our drugs. Without drug treatments, tuberculosis kills about 45% of patients, and nearly everyone who is HIV positive.
Gonorrhoea, a sexually transmitted infection, used to be treated with penicillin but, as recent outbreaks in the UK have shown, the bacteria that cause it have developed resistance to all but one antibiotic, and even that is starting to become less effective. Untreated, gonorrhoea can lead to infertility and inflammatory disease. Drug resistance makes infections more serious, harder to treat, and a bigger threat to our lives.
Who is at risk?
We are all at risk if infections that are currently easily treated become resistant to the small number of drugs we can still use. For some infections, it might mean just an extra day or two of feeling ill, but it could also increase the risk of death, especially for vulnerable patients like young children.
Drug-resistant infections already directly cause an estimated 700,000 deaths each year. It's expected that will rise to 10 million a year by 2050. If nothing changes by then, this scale of human suffering and premature deaths will have set the world's GDP back by as much as 3.5%.
But we also use these drugs to help control infections during and after surgery, including organ transplants, hip replacements and caesarian sections. As more infections become resistant to our drugs, even routine operations will become riskier.
Can't we just make new drugs?
One way to get around the emergence of drug resistance is to keep inventing new drugs that exploit different weaknesses of the infectious species. But the rate of development of new antibiotics (and drugs for treating viral and parasitic infections) has slowed since the 'golden age' of the second half of the 20th century, exacerbating a problem that has been known about since the discovery of penicillin in 1928.
Current business models do not incentivise the development of new antibiotics. Development costs are high, and are very hard to recoup because the drugs cannot generally be sold either at high prices or in high volumes. When a new antibiotic does reach the market, medical stewardship requires it to be used sparingly and only when absolutely necessary to delay resistance from developing, but reimbursement models do not currently reward this.
To reinvigorate the development of new drugs for infections, we need to make the discovery and invention of antibiotics a game that everyone is incentivised to play, in universities, pharmaceutical companies, government research labs or anywhere else.
What else can we do to counter drug-resistant infections?
We need to look after the drugs we already have. This means using them properly – saving antibiotics for bacterial infections they can treat, and not using them to 'treat' viral infections like the flu and the common cold.
Misusing antibiotics like this essentially breeds drug resistance among the bacteria that normally live in our bodies – even though these bacteria are harmless, they can pass resistance on to other, more dangerous species.
The same is true if people don't finish their course of antibiotics, or when antibiotics are used in agriculture as growth factors or preventive treatments – it all breeds stronger, more dangerous bacteria.
So we also need better diagnostic tools to tell doctors exactly what is the cause of their patient's infection so they can prescribe the most appropriate and effective drug. And, as potential and actual patients, we all need to understand how to make the best use of the drugs we are given to treat infections.
Should we invest more in alternatives to drugs?
Drugs are not the only tools we have to tackle infections. Improving access to clean water is helping to eradicate endemic Guinea-worm disease in the absence of any drugs. For other diseases, we have effective vaccines that prevent illness and can help to stop the spread of the infection. One way to reduce the impact of drug resistance would be to develop vaccines for more infections, and to use the vaccines we have to systematically control or eliminate those diseases. However, there are still several infections for which we do not have vaccines, and drug treatment is the only effective response.
Who is responsible for responding to drug-resistant infections?
Infectious diseases are a public health issue. Drug-resistant infections span political borders and require coordinated action from authorities around the world. But we must all take on some responsibility for understanding the problem – which will always be with us as long as we use drugs to treat infections – and the simple things we can do to avoid making it worse.