Some bacteria have evolved resistance, creating a growing army of “superbugs” against which there is no effective treatment. Antimicrobial resistance is expected to kill 10m people a year by 2050, up from around 1m in 2019.

But there is a promising, if obscure, alternative that is also worth a look. Microbiologists have known for decades that disease-causing bacteria can suffer from illnesses of their own. They are susceptible to attack by bacteriophages (“phages” for short): specialised viruses that infect bacteria, and often kill them.

Using one disease-causing organism to fight another has several advantages. Like antibiotics, phages are picky in their choice of target, leaving human cells alone even as they infect and destroy bacterial ones. Unlike antibiotics, phages can evolve just as readily as bacteria can, meaning that even if bacteria do develop resistance, the phages may be able to evolve around it in turn.