Parvovirus In Dogs

I'm a resident of New york, USA and my dog tibetan terrier's health has been a cause of concern for me since last three days. It has observed a loss of appetite and has vomitted twice since yesterday. I took him to the veterinary and he suggested some medications but it has shown no signs of recovery yet. I've heard of a disease called Parvovirus in dogs having similar symptoms which my dog going through right now. I want you to tell me all about this disease, it's symptoms, what test my dog will have to go through to detect this disease? If this disease can be fatal or not? Please give me the details soon.