Lefheim-Vector Disease

A disease that affects the brain, causing the host to only think of lust, mainly from fiction. Anyone who has it loses control over themselves and commits various actions once their sight is set on a fictional person. Many have succumbed to the disease, locking away the outside world, all for their one true fictional love.

Person 1: "I know she's not real, but I can't stop looking at her picture!"
Person 2: "Sounds like the Lefheim-Vector disease to me."