The markets have been bungling along in fairytale land for quite some time. I'm surprised it took this long for the markets to react significantly.
The danger in COVID-19 is that it may be a precursor that weakens the host immune system and increases susceptibility to an evolution from COVID-19, or some other new pathogen, that requires a particular level of host susceptibility and the right environmental conditions for it to be lethal.
There are some interesting factors here that bear similarity to the "Spanish Flu" which killed 50 - 100 million people. COVID-19 will not be that type of virus, but something else could emerge which does.
Prevalence of human coronaviruses in adults with acute respiratory tract infections in Beijing, China
Is Covid-19 a precursor virus rather than the main event?
Antibody against nucleocapsid protein predicts susceptibility to human coronavirus infection.
The identification of a new coronavirus now named Covid-19:
Recovered patients may still be contagious and transmit Covid-19:
A person showing no symptoms can pass the coronavirus to others:
Misreading the story through numbers: