Should I get a lawyer?

I was tested for MRSA at the emergency room. While waiting on the results, I needed to see my dentist. I decided, I should put it in my medical history just in case my test came back positive. I also told the dentist out of respect for his staff. Well, months later, I referred my roommate to this dentist and the dentist actually felt he should warn her that I had MRSA. Does the dentist have a right to do this. I do not have it but the hospital administrator told me if I had, they would have called me and notified the Department of Health.