If you follow the link to the Nature paper, it answers your questions in detail, including statistics concerning the 15 genome sequences in question. You come across as uncaring to the people that may have a susceptibility?Yes, I agree... I guess there are more worrisome risks for me, like getting hit by meteorite(also not zero).
How many healthy people under 60 in the whole world do you think have previously contracted and easily overcome the virus only to die the following year by contracting it again?
I have no idea about your second question.