If a person sick with the flu, God forbid, sneezes into my mouth, I know that I now have a chance of getting sick myself.  But people in the olden days didn’t always understand the infectious disease.  As we know, “flu” is short for influenza.  Influenza is Italian for “influence.”  This refers to the accepted cause of the disease at the time; they thought that the illness was caused by astrological influences.  People were so dumb.  I can say this without feeling bad, because I know that in 400 years people will look back and talk about how dumb our leading scientists and doctors were.  Science enables people to be condescending to their ancestors.