 It's a lesson for the ages. And yet there's always surprises. And it seems to me in reading your book that one of the surprises to you perhaps is that the science has not yet allowed us to figure out that we can develop a vaccine or if we might be able to develop a vaccine or when we might have a vaccine. I wonder if you'd like to talk about that in terms of for all the science and the tools we have, there are certain things that we just have not yet been able to do with regard to this.