Well, thanks for being willing to update your priors. It's rare to find that. I should noted that technically it is "grad and professional students", just to be scrupulous, but when I got my PhD not so long ago, "grad student" generally included professionals unless otherwise specified. But the number of "grad students proper" (people getting PhDs) at Duke is very likely still in the several thousands, so even conservatively, it's an infection rate around one percent, much lower than undergrads. That said, I have no good answer to this puzzle.
I used their web site. It could well be 9,000, so my point is incorrect.
Well, thanks for being willing to update your priors. It's rare to find that. I should noted that technically it is "grad and professional students", just to be scrupulous, but when I got my PhD not so long ago, "grad student" generally included professionals unless otherwise specified. But the number of "grad students proper" (people getting PhDs) at Duke is very likely still in the several thousands, so even conservatively, it's an infection rate around one percent, much lower than undergrads. That said, I have no good answer to this puzzle.