There is a passage in the movie Resident Evil 3.
"Doctor, when will those monsters on the ground disappear completely?"
"Sir, if all conditions remain unchanged, the control ability of T virus will be around 15 to 20 years."
"You mean I have to stay here for 20 years? I've had enough. I really don't know what you idiots do. "
"This is just a conservative estimate. If zombies have been involved in eating, it may be longer ... "