A Delta Quadrant species, largely assimilated by the Borg, whose survivors infected a cube with a synthetic pathogen that later afflicts Seven of Nine in Infinite Regress.
Species 6339 is known only by its Borg designation and appears in the Voyager episode Infinite Regress. The Collective had assimilated most of its people about four years before the events shown. The survivors designed a pathogen to attack a vinculum, the device that links the minds aboard a Borg vessel, and thirteen volunteers allowed themselves to be assimilated in order to carry it.
The plan worked on one cube, which destroyed itself. In 2375 Voyager finds the debris and brings the still active vinculum aboard. Its signal awakens the personalities of people Seven of Nine once helped to assimilate, and they take turns controlling her.
A ship of Species 6339 arrives under Captain Ven and demands the device back, so that the infection can spread to other cubes. Janeway returns it once Tuvok has reached Seven through a mind meld.