The figures I saw (BBC article reporting on research paper from China) showed high risk for elderly. If you're young and not afraid, that's fine: a 0.2% death rate for those in their 30s backs that feeling up. But people in their 80s have a 15% death rate, which is hardly flu numbers.
Investments aren't solely about this being a bad flu, either. Look at how governments respond: China locks down a region with tens of millions of people. Nobody going to work, no malls open.. nothing. Empty streets. With countries not allowing travelers from China, a huge number of tourists aren't traveling. When a new city gets the virus, that city gets locked down... and then travel plans get canceled.
This week stocks dropped almost -8%, which is more in line with SARS (from one source that I haven't verified). But with all the economic disruption (like supply chains with parts / components from China), I don't see how this could be the same as SARS. If the markets are relatively calm in March, while COVID-19 continues, I'd expect a lot of stock market panic when the data comes out (2020 Q1 reports by companies).