Quarantine is the practice of isolating individuals, places, or things that carry a potentially dangerous ailment.
As part of the quarantine, red flashing beacons on the hull of the ship where turned on and the following message was repeatedly broadcast on all frequencies:
- "Extreme caution! The USS Lantree is a quarantined vessel by order of Starfleet Command. Do not board!"
When Willie Potts was tricked into hiding due to his brother, Jake Potts, on Ogus II in 2367, Willie accidentally ingested parasites from a cove palm. In order to get medical assistance at Starbase 416, Willie had to be placed in quarantine. (TNG: "Brothers")
In 2369 after several crewmembers including Miles O'Brien and Jadzia Dax suffered from the aphasia virus, Benjamin Sisko told Doctor Bashir that he wanted DS9 under emergency quarantine. (DS9: "Babel")
In 2373, an Antidean transport's cargo was being held in quarantine aboard Deep Space 9. Doctor Julian Bashir was required to issue a health certificate to remove it. (DS9: "Doctor Bashir, I Presume")