Re: What is the difference
A couple of thoughts - there are, despite the PC view, some small genetic differences between races, in addition to visible ones. This means that there is a possibility that some diseases might have a greater or lesser effect depending on race, if it somehow involves these small differences.
However, this would usually take a long time to become prevalent. Sickle cell anemia, Crohn's disease, etc have been affecting populations for many generations.
I think the ways SARS has spread has more to with cultural and/or government that race, but it would be worth some research.