well they have to know you know how to diagnose there patients wether they had phneumonya or the flu most of the time if there testing for flu there going to have to put a swab up the nose to collect the snot and then they put it into a silender type thing and thats how they diagnose you with flu.phneumonya its a little bit different they can tell by your symtoms that you tell them and then to treat it they give you either pills or a shot in the neck thats how they learn how to professionaly diagnose you with things hope this helps.
