How did the black death travel from sarai to cairo

The black death had traveled through trade routes

Ongoing civil wars western roman empire finally collapsed476 c.e. romulus, the last of theroman  emperors in  the west, was overthrown by the germanic leader odoacer, who became the first barbarian to rule in rome. the order that the  roman empire  had brought towestern  europe for 1000 years was no more.

:what is edwards's purpose for giving this sermon? which elements likely make the argument effective for a puritan audience?