In February, an exciting threshold in medical history was crossed: a team of scientists at the University of Pittsburgh used contemporary gene editing tools to alter a bacteriophage. The phage ­­— a tiny organism that preys on bacteria — was then used to treat a young English woman, Isabelle Holdaway, who was suffering from a previously untreatable bacterial infection.

One of the scientists to identify this moment as historic was Steffanie Strathdee, an infectious disease epidemiologist at the University of California San Diego (where she heads up a phage research and treatment program called IPATH) and the author of The Perfect Predator: A Scientist’s Race to Save Her Husband from A Deadly Superbug (Hachette Books, 352 pp.).

That titular race played a key role in sparking the recent wave of renewed interest in phages. Strathdee’s experience was, as her book’s title suggests, horrific. Her husband contracted a superbug infection while travelling in Egypt and was saved by an eleventh-hour intravenous phage treatment. But — as she put it when we spoke to her about her book, phage technology, and the looming superbug crisis —

“it wasn’t really until my husband’s case hit the news” that phages caught the interest of the medical mainstream again. “He was treated with phage therapy in March of 2016. In April of 2017, the results were presented at the Pasteur Institute for the 100th anniversary of the discovery of bacteriophages.”

This wider medical recognition is long overdue, in Strathdee’s opinion. “Phages,” she told us, are “actually the oldest and most ubiquitous organisms around. It’s estimated that there are ten million, trillion, trillion phages on the planet. They’re in soil. They’re in water. They’re on our skin. They’re in our guts.” Despite this ubiquity, their potential use as an anti-bacterial agent was not discovered until 1917. A French biologist and entrepreneur, Felix d’Herelle, managed to isolate them and use them to treat dysentery. While d’Herelle’s discovery soon fell into the shadow of the discovery of penicillin, phages went on to enjoy a robust medical use in the Soviet Union and in some European nations. However, the medical uses of phage, Strathdee explained, were largely ignored in the U.S. and elsewhere — even as the tiny organisms proved to be foundational for much of modern microbiology.

“About half of the Nobel Laureates in the 1950’s and 60’s won because of their work on phages,” she points out. “But they were seeing phages as a tool. They were never really forgotten in basic biology, but they were forgotten in medicine. Even with CRISPR [a powerful contemporary gene-editing tool], phages were used as a tool to discover it. CRISPR is really a form of the bacteria’s immune system that they equipped themselves with to protect themselves from phages.”