“A Boston patient tested positive for SARS-CoV2 infections four separate times over 22 weeks. He was admitted to the hospital six times, including stints in intensive care. Swabs taken from his nose and throat during his second hospital stay provided the first hint of the virus’ startling pace of genetic transformation: Compared with a sample taken during his first hospitalization, 11 letters in the coronavirus’s 30,000-letter sequence had flipped, and nine such nucleotides had dropped out.
His next trip to the hospital landed him in the ICU. Tests revealed that 10 more letters in the virus’ genetic code had changed and one more had been deleted in a period of just five weeks. Three weeks later, after he had seemed to recover, he tested positive again and was put on a mechanical ventilator to help him breath. This time, researchers found 11 more letter changes and 24 more deletions in the virus’ genome.