Pathogen, ID: 240299. Virus-like microorganism, takes the appearance of a thick fog. Point of entry: inhalation, affects the amygdala of the brain. Symptoms: restlessness, anxiety, vivid hallucinations (individual and group-wide), deep sleep.
Origin: Unknown, was found abandoned by a patrol. It arrived in a glass capsule to the Starbase 777 for study; it was involved in a station-wide incident, on Stardate 91892.1.
Avoid inhalation. Exposure to clean air can flush the organism out of the affected body. Usage of gasmasks or anything else that can filter particles out of the air, is strongly advised.
Note: Prolonged exposure is dangerous not only for it's hallucinogenic properties, but also it's apparent ability to manifest in a physical manner to pursue it's victims. While it's properties can be interpreted as malicious intent, there was no feasible way to test it's possible sentience - the experiment being deemed too dangerous. Proceed with utmost caution! -- Lt. JG. tr'Lareth.