Obsession is a symptom in the Neurax Worm DLC. It causes severe damage to the orbital cortex, triggering OCD (Obsessive-compulsive disorder). It forces the host to obsess over a worm-related task.
There are three possible obsessions. The following are listed and described below:
Eradicating parasitic worms
The most common, which causes Neurax Worm hosts to give a boost to cure development.
The second most common, humourous one. It does nothing to help the cure but increases infectivity(+20), it merely makes hosts obsess over earthworms.
Avoiding parasitic worms
The rarest of the three, which decreases infectivity（-20）, making it lower than before evolving the symptom.