I will say it caused more than 300k.
That conference was the cause of the breakout in Indiana. At least the known break out. Could have been there before that but the conference started the rapid known breakout.
I think Indiana had several people that got it from that conference.
So if you extrapolate - there had to have been more States that got infected from that conference.
That was the conference after which a chinese woman {who reminds me of Fang Fang} took a bunch of pills to suppress her fever and fled the conference and the US