Brief Description:
The "Middle Passage" is about enslaved American Americans that were transported to the "New World."
Answer:
In bad weather the oppressive heat and noxious fumes in the unventilated and unsanitary holds caused fevers and dysentery, with a high mortality rate. Epidemics were a major cause because of the New World's diseases. People got sick, and didn't have the medicine to treat it, because they don't know what disease it was.
( Sorry if this didn't help, this is all I know about the "Middle Passage." )