Virologists here have noticed that people can be infectious before showing any symptoms. The mortality rate is 2-3% whereas seasonal ‘flu is less than 1%.
People with most kinds of respiratory viral infections (or even chickenpox) can be infectious before showing any symptoms.
It is surprisingly hard to estimate the true case-fatality ratio of rapidly spreading respiratory infections like influenza or the ongoing novel coronavirus outbreak. A substantial number who get the infection have mild or no symptoms, are never diagnosed, and are therefore not counted in the denominator of the ratio.
Also, for seasonal influenza, the majority of deaths are in older individuals with pre-existing health conditions. It is not yet clear whether this is true for the new coronavirus. At least, there is no firm evidence yet that the coronavirus is mutating rapidly (unlike for example, the H5N1 avian 'flu virus), which seemed to quickly become increasingly severe after making its first "jump" from birds to humans.
Sensible precautions are fine, of course, but I wouldn't be too worried (at least yet).