So someone I know was diagnosed with obsessive-compulsive disorder. Anything I should be aware of? 
Well it is a mental disorder where people repeatedly check things, are very routine, and have certain thoughts repeatedly. 
Oh I see. Is there different severity levels to it?
following infections. The diagnosis is based on the symptoms and requires ruling out other drug related or medical causes. Rating scales such as the Yale–Brown Obsessive Compulsive Scale (Y-BOCS) can be used to assess the severity. Other disorders with similar symptoms include anxiety disorder, major depressive disorder, eating disorders, tic disorders, and obsessive–compulsive personality disorder.
Treatment involves counseling, such as cognitive behavioral therapy (CBT), and sometimes antidepressants such as selective serotonin reuptake inhibitors (SSRIs) or clomipramine.
Obsessive–compulsive disorder
Obsessive–compulsive disorder (OCD) is a mental disorder in which a person feels the need to perform certain routines repeatedly (called "compulsions"), or has certain thoughts repeatedly (called "obsessions"). The person is unable to control either the thoughts or activities for more than a short period of time. Common compulsions include hand washing, counting of things, and checking to see if a door is locked. Some may have difficulty throwing things out. These activities occur to such