1. The R0 of the disease sets the percentage at which herd immunity sets in and the virus stops spreading. The flu has a much lower R0 than the coronavirus. 3.

1. The R0 of the disease sets the percentage at which herd immunity sets in and the virus stops spreading. The flu has a much lower R0 than the coronavirus. 3. Because it's much worse than the 2009 flu on almost every metric. If we treat them the same, there will be two orders of magnitude more deaths.