1. Quarantining 50,000 people qualifies as a "major impact?" There's a bit of hyperbole in that article and in your argument. Everyone is extrapolating to a "what could be" scenario and the truth is we have no idea how much worse it can/will get. It could spread and become a true pandemic or we could be seeing the worst of it right now and deaths will be limited to no more than 5,000, only time will tell. But for markets to price in a truly disruptive scenario with global recession implications is definitely betting on the extreme. To say the US is doing nothing is also a lie as we've restricted travel, are actively investing in treatment options, and are working hard to track down cases and isolate the spread.
2. I said the mortality rate was lower than other diseases we've battled in the past decade. SARS was 11%, Ebola 83-90%, MERS 45% (your source: https://en.wikipedia.org/wiki/...), and COVID-19 at 2-4%. Most deaths have been in humans with compromised immune systems or preexisting conditions that made increased their likelihood of death from just about any infection.
Please provide your reference for US deaths in the millions if this disease actually spreads here? China appears to be plateauing, has more than 4 times our population, and has a total of 2,788 deaths as of this writing (https://vac-lshtm.shinyapps.io/ncov_tracker/).