Blue Shadow Virus/Legends

The Blue Shadow Virus was a devastating virus that plagued the galaxy generations before the Clone Wars.

Characteristics
The Blue Shadow Virus was notorious for being able to affect every species in the galaxy, was said to be completely fatal, and supposedly had no cure. It was a waterborne virus.

Its name may have been derived from the blue hue that infected corpses of many species developed. The virus ran rampant across the galaxy several generations before the Clone Wars. To the relief of the general public, it was eventually eradicated.

History
During the Clone Wars, however, a mentally unstable scientist, Dr. Nuvo Vindi, recreated the plague. When Jar Jar Binks and Padmé Amidala were captured, he claimed the virus was not eradicated, but murdered. He also claimed he had recreated life: the life of the virus. Though the virus originally spread through water and killed certain species instantly, Vindi was able to create an airborne version. The airborne strain's incubation period was longer than the waterborne varieties. Respiratory symptoms preceded death.

Jar Jar and Padmé tried to convince Vindi of the danger of releasing the virus, but he refused to listen and attempted to release the virus anyway. However, a detachment of the 501st Legion was dispatched, and the laboratory was successfully secured. However, Vindi's servant droid LEP-86C8 was soon able to detonate one remaining bomb, infecting Padmé, Ahsoka Tano, Rex and many clone troopers. Before the virus could kill everyone trapped in the laboratory, Anakin Skywalker and Obi-Wan Kenobi were able to find the cure, the Reeksa root. After obtaining enough of the root from Iego, the infected were cured.