Usually when a person is infected by a disease, they will first visit a nearly hospital or dispensary. In medical terms the first doctor he meets is called something specific.
I remember this word from the book by Richard Preston called
The Hot Zone which was about an ebola outbreak many years ago.
Edit: General practitioner is definitely not the word I'm looking for. I am aware of all the terms such as GP, specialist, consultant etc. The word, or term I'm looking for addresses the first point of specialized care a patient encounters. This is called something along the lines of 'initial medical entry point', and the doctors at that point will try their best to contain the disease without letting it spread, based on the diagnosis. Sorry for any confusion.