SARS-CoV-2, the coronavirus that causes the disease COVID-19, is a big viral family with many variants. Just like with a human family tree, the distance between two variants shows roughly how related they are. This illustration is inspired by the SARS-CoV-2 phylogenetic tree generated by Emma Hodcroft of Nextstrain.org and the University of Bern. Her tree is reproduced within the story below. (Kat Hubbs for NPR)
