Is Covid’s friendly little cousin the future of medicine?

Since the pandemic, viruses have got a bad rap. Sars-CoV-2 is a nasty little critter, to be sure, but the vast majority of viruses do no harm to humans. And a large class of them might even represent the future of medicine. One day, people with stubborn infections might be prescribed not an antibiotic pill but a little glass vial full of viruses. Tasty.

Our instinctive unease at that idea is just one of the problems that remain to be overcome, however, before it becomes a mainstream solution to the increasingly pressing problem of antibiotic resistance. Our incontinent use of antibiotics, not just in humans but in farmed fish and cows, too, has effectively selected for breeds of bacteria that are immune to them: hence dangerous superbugs such as MRSA. No new antibiotic classes have been discovered since the 1980s, and the big pharma companies are not racing to find more: there’s not enough money in it.

Enter the hero of our story: the bacteriophage virus, or phage for short. So named upon their discovery in the early 20th century because they feast (from the Greek “phagein”, to eat) on bacteria, phages might be the most numerous lifeform on Earth: “around a trillion phages for every grain of sand on the planet”, it says here. They regulate our gut microbiome, are crucial to marine ecosystems, and inspired the modern Crispr technique of gene-editing: they are eldritch marvels of natural nanotechnology, festooned with what look like arms and heads and tiny drills to inject a bacterium with their DNA and force it to create copies of itself before bursting apart.  

Hence current hopes for “phage therapy”, building on an undercurrent of maverick research and experimentation over the past century, since their discovery in 1917 by the gadabout French-Canadian biologist Felix d’Herelle. Phage therapy was trialled in Soviet Russia and successfully employed by heroic scientist Zinaida Yermolyeva to treat wounded soldiers at the siege of Stalingrad. Western medics flirted with the idea but largely abandoned it – and banned the use of phages – after penicillin became widely available. 

To this day, however, phage therapy is still permitted in some outposts of the former USSR. A leading clinic in Tbilisi, Georgia, receives requests from all over the world for phages to fight resistant infections, and in recent decades mainstream science has turned back to investigating their therapeutic uses. Phages, new research suggests, are not merely good at killing specific bacteria; they are such exquisite machines that they might be the perfect vehicles for cancer drugs to target tumours.