We hear it often: Delta's more transmissible, maybe deadlier; it's easy to jump to conclusions about why there might be a link between those traits.

But viral evolution isn't that simple. Me, on the complexities of virulence and the future of variants:https://t.co/lWXWuVohte

— Katherine J. Wu, Ph.D. (@KatherineJWu) June 28, 2021