Absence of mind is catching. Or rather it's swarming. A hive of it has exploded and now the bits and pieces are looking for a new home. Unlike bees they don't need a queen. Each piece can find a mind and start a new home, multiplying it's forgetfulness until you can't even think of your own name or age (forgetting one's age isn't necessarily a bad thing, though it can prove embarrassing).
I think I've been infected.