In the days before COVID-19, I’d often get frustrated by the response that doctors would give when I turned up at their clinics with some infection or other: “It’s just a virus,” they’d say.

As someone who’s long been fascinated by the detective work that goes into tracing the origins and history of infections, the answer always seemed too perfunctory. Which virus was it? Where and when did this strain emerge? How many other people were getting infected with this same variant this year?