Encountered by USS Voyager in 2371, the Vidiians suffer from a disease known as "the Phage" which attacks every part of their bodies. The humanoid citizens of the Vidiian Sodality first fell victim to the fatal viral disease known as the phage 2,000 years ago. The effects of the phage were devastating and the society of artists and intellectuals were soon forced to devote all their energies to finding a cure.
In two millennia, the Vidiians have made little progress in their search. Thousands die each day as the deadly disease
destroys genetic codes and cellular structures. The Vidiians have no cure for the Phage, and are forced to replace body parts on a regular basis. To fight the phage's ravages, the Vidiians have become dependant upon the harvesting of organs from other races. They may have originally sought to use the bodies of the recently deceased, but they now regularly take organs from living bodies. The constant battle with the disease has had an effect on Vidiian morality and has led them to take life and imprison others without remorse. Despite possessing advanced medical knowledge, including genetic engineering, the Vidiians apparently lack the ability to clone bodies for replacement parts. They therefore frequently attack other species and steal their organs for transplants.
The Vidiians feel that their behaviour is justified because the organs from one victim can provide life for a dozen
Vidiians. The value of organ 'donors' is maximised; they are often kept alive in captivity and used over a period of
time. The phage has led to the Vidiians to develop extremely sophisticated medical technology. Vidiians can
biochemically alter air-breating organs and have advanced immunogenetic technology. They can isolate and extract DNA sequences Vidiian databases hold the cures for thousands of diseases and conditions. However, they are still unable to find a cure for the phage or even a vaccine. This has led to the average Vidiian having a wide variety of alien organs and skin on their body, resulting in a hideous 'Frankenstein' appearance. Voyager first encountered the species when two Vidiians stole a lung of Neelix whilst he was on an away mission, and have subsequently attacked the ship or crew on several occasions. Vidiian technology is generally in advance of that of the Federation, making them formidable opponents.
Voyager passed out of Vidiian space sometime after late 2372 but although there was no further direct contact, this was not the last the Federation ship has heard of the species. In 2375 Voyager was contacted by the "Think Tank", a small group of aliens who specialize in solving problems for other species. The Think Tanks representative, Kurros, informed Captain Janeway that his group had recently found a cure for the Vidiian Phage. It can only be hoped that with the end of this great burden on their civilization, the Vidiians returned to the peaceful people they once were two millenia ago.