When fears of contagious diseases such as avian flu and ebola arise, public health officials encourage people to replace greetings involving close contact (handshakes, hugs) with an elbow bump. this change in greetings represents a shift in?

Social norms.
Norms are like informal guidelines that are understood as important to act and behave on a specific society with its cultural beliefs. Being part of a society or culture establishes certain beliefs that lead us to a certain behaviour as social norms. In this specific case, living in an emergent potential risk of a contagious disease, created such norms.

Yes you need to call another ambulance because you need to take care of someone with a broken arm , head injury (also unconscious) you would need another ambulance to check on the pregnant woman and man with cuts and scratches.