The Garan mining colony was a Delta Quadrant settlement whose distress call led Voyager to a macrovirus outbreak in 2373, an infection that soon overran the ship itself.
The colony appears in the third-season episode Macrocosm. Voyager answers its call for medical aid, and the Doctor, making an early outing with his mobile emitter, beams down to find the miners suffering from a virus that grows large enough to be seen and then to fly.
A sample is carried back through the transporter and spreads through the ship's bio-neural gel packs and crew. By the time Janeway and Neelix return from a trade mission to the Tak Tak, the corridors are full of buzzing macroviruses and everyone is incapacitated.
Janeway fights her way through the ship while the Doctor synthesises an antigen. She lures the organisms to the holodeck with a simulation of the Paxau Resort and releases the cure there.