MRSA is a very lethal contagious flesh eating bacteria. My dad has had a black spot on his inner thigh for a couple days and today he just got confirmed by his doctor to have MRSA.
That's kind of overstating the lethality of MRSA. People who contract it in the form of a skin boil basically never die.
The reason why it's so deadly is the fact that a lot of the people who catch it already have serious illnesses, since it gets spread around in hospitals. Another reason is the fact that many of those aforementioned people catch it in the form of pneumonia, and it gets way worse before they even figure out that it's MRSA. At that point, it's very difficult to treat it.
I'm not saying this to minimize your dad's case or anything, but you don't have very much to worry about.