LONDON All at once, the coronavirus seemed to change.
For months, Dr. Steven Kemp, an infectious disease expert, had been scanning a global library of coronavirus genomes. He was studying how the virus had mutated in the lungs of a patient struggling to shake a raging infection in a nearby Cambridge hospital, and wanted to know if those changes would turn up in other people.
Then in late November, Dr. Kemp made a startling match: Some of the same mutations detected in the patient, along with other changes, were appearing again and again in newly infected people, mostly in Britain.
Back in March, researchers decided to routinely record the genetic sequences of the virus they found, giving them a powerful tool for tracking mutations.