I thought the way pathogens of zoonotic origin evolved is deadly/hard-to-catch -> evolution -> less-deadly/easy-to-catch. SARS was not this contagious. How is this new coronavirus so incredibly contagious straight out of the door? There was no human-circulating sars-like virus that this evolved out of, it just immediately jumped from another species to humans at contagion level 9000? Are there any other examples of epidemics that have acted in this way?