I found the following couple of hadiths from the Sahih Bukhari:
Volume 9, Book 87, Number 162: 
Narrated 'Abdullah bin 'Umar: 
concerning the dream of the Prophet in Medina: The Prophet said,
 "I saw (in a dream) a black woman with unkempt hair going out of Medina and settling at Mahai'a. I 
interpreted that as  (a symbol of) the 
epidemic of Medina being transferred to Mahai'a, namely, Al-Juhfa." 
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Volume 9, Book 87, Number 163: 
Narrated Salim's father: 
The Prophet said, "I 
saw (in a dream) a black woman with unkempt hair going out of Medina and settling in Mahai'a. I interpreted that 
as (a symbol of) epidemic  of Medina being transferred to Mahai'a, namely, Al-Juhfa." 
Why a black woman?
What does a dream of a black woman have to do with the spread of an epidemic?  
