Mr Yun writes:
There has been speculation as to why the Forerunner would keep the Flood alive.
Considering that the Forerunner are an advanced species, we should be more surprised if they completely erradicated the Flood.
Think about it, what kind of idiotic race kills an entire species just because it is dangerous (present company excluded, of course)?
Why not kill all tigers and snakes and alligators and sharks too? (yeah, I know we're trying.)
Well, heres why you shouldn't eliminate every species that is apparently bad: You never know what the future may hold.
Even humans, a moderately advanced race, keeps live specimines of everything from cholera to ebola. During the 1990's we tried to resequence and revive the Spanish Flu (1918 flu), that killed 100 million people world wide...in one year.
So it should be ASSUMED that the Forerunner would keep specimens of the Flood for research. Maybe they could prevent another species from evolving into the flood in another 1 billion years. The Forerunners were thinking ahead...they're supposed to be smarter than us.