Zombies bite medics

I was sitting in an infection control class today for the rescue squad I volunteer with.  We were talking about what to do if a patient bites us and draws blood.  There is a federal law that requires the source of the blood to be tested for a battery of blood borne diseases.   He then proceded to say that nothing can be contracted from saliva so the patient would not be tested.  When hearing this I muttered under my breath that nothing could be contracted from the patients saliva unless of course said patient was in fact a zombie.  I got a few laughs from this, but if you think about it the only reason I could think a patient would bite a medic dispatched to help them would be if they were a zombie.... or just plain crazy.  If a patient bites me and is not crazy or a child then they are going to get punched in the head.  What actually are the chances of a zombie apocalypse actually happening.  Honestly if one happened it wouldnt exactly surprise me.