There are, but they are so similar as to barely deserve recognition as separate strains - just two genetic "letter" differences, and one amino acid (S and L are the amino acids that have changed, nothing to do with serious/light). S strain seems to be the original one, L strain now outnumbers it 2:1. It's not yet clear quite how that relates to virulence and transmissibility, it could just have been luck that someone with L strain sneezed at a football match.
See this paper :
On the origin and continuing evolution of SARS-CoV-2
Pretty much all the deaths in Italy have been of people with other conditions, which may reflect that the doctors are overwhelmed and having to play God with who gets ventilators. I'm not aware of any evidence that it's getting more virulent.
The "common cold" is not one virus, lots of different viruses cause symptoms that are similar, so the problem is not so much serial "mutations" of the same virus just that your immune system can't keep up with the huge population of different kinds of virus (although mutations are part of the story, more on a year-to-year basis though). Coronaviruses other than SARS-CoV-2 are one of the groups that do cause cold symptoms, but they're a small minority.