The greatest disease is not in the flesh, but in the feeling of being unwanted. image - Star Trek: Armada 3 mod for Sins of a Solar Empire: Rebellion

The Tarellians are a species teetering on the very edge of extinction. In the early 24th Century a civil war on their home planet of Tarella unleashed a deadly bioweapon - a plague that spread gradually across their world and eventually infected their entire species. Over the decades the Tarellian population dwindled while a cure remained elusive, and hope for Tarella seemed lost.

Having achieved basic interstellar flight, many Tarellians travelled to other worlds in desperation. They unknowingly carried the plague with them, and eventually died alongside those who had been generous enough to take them in. The surrounding worlds began turning the Tarellians away in fear, and eventually more pragmatic, less compassionate species began hunting down and destroying Tarellian ships.

Now, years pass between sightings of the few remaining Tarellians, and a cure for their affliction has still not been found. While they intend no harm, the stories of the Tarellian Plague have not been forgotten. The mere proximity of a Tarellian ship is enough to cause widespread panic among a planet's population. Starfleet is under standing orders to turn the Tarellians away wherever they appear, using as gentle means as possible. That said, force can be applied should they not take no for an answer - an unfortunate and unpleasant prospect that any Starfleet captain could face when encountering the Tarellians.