What is the significance of Mercutio's statement, "A plague o' both your houses!," in Act 3, Scene 1 of Shakespeare's Romeo and Juliet?

Mercutio's declaration, "A
plague o' both our houses!," immediately after being fatally stabbed by Tybalt, is
significant because it characterizes just how much
damage the feud between the Montagues and Capulets is
causing. Plus, more importantly, Mercutio's line significantly expresses
his own feelings about the feud, feelings that the audience
echoes at this point in the play.

We know that
Mercutio's line is a significant reference to the two families' feud because the phrase
"both your houses" refers to both the Montague and Capulet households. More importantly,
the term "plague" characterizes how much
damage the feud has caused. The term "plague" can have a
double meaning. Plague can refer to an
epidemic disease that is causing a significant number of
deaths (Random House Dictionary). In this sense, Mercutio is wisely stating the obvious
that both households have a disease of the mind due to their longstanding hatred and the
hatred, like a plague, is causing a significant number of deaths, like Mercutio's.
But "plague" can also refer to a curse. In this sense,
Mercutio is cursing the two households, meaning wishing
that both households will be affected by "misfortune" or ill fate in consequence of his
death as well as anyone else's death the feud has already caused ( href="http://www.shakespeare-online.com/plays/romeo_3_1.html">Shakespeare-online).
Cursing the households also expresses his feelings
concerning the feud--the feud has just taken his life; therefore, he very naturally and
understandably sees the feud as despicable, something that Shakespeare
wants the audience to see as well.