At the height of the Vultrumite Empire, their enemies sought a way to end their campaign. Since they could not best them in combat, they created a virus that was unique to the Vultrumite's genetic code.
The First Strain
The first strain of the virus killed Vultrumites at an alarming rates. All attempts to quarantine the infected failed and the entire planet of Viltrum became infected with the disease. Some were able to survive through the virus, but found that they had sustained a temporary after-effect where their strenght and invulnerability was greatly diminished. With the deaths from the virus itself and the deaths from weakened Vulrumites the Vultrumite Empire had lost 99.9% of its Vultrumite population, leaving less than fifty alive.
The Second Strain
The second strain was created on the orders of a survivor of the original strain, Thaedus. Thaedus had turned his back his back on the Viltrumite Empire and became the leader of the Coalition of Planets, a group formed to fight the Vultrumites. He offered a sample of his cells to his scientists so that they could take his anti-bodies from the first virus and produce a new version that could kill the remaining Vultrumites. After the events of the The Vultrumite War, the remaining Vultrumites had returned to Earth and were going to be allowed to breed with humans. This would raise a brand new Vultrumite army to combat the Coalition yet again. This was unacceptable to new Coalition leader, Allen who vowed to use the new strain on Earth even though it would kill the humans on the planet as well, due to their genetic similarity to Vultrumites.
Allen then came to Earth with a single canister of the virus and Oliver Grayson at his side. Upon arrival in orbit they are stopped by Invincible and Thragg. Thragg tries to reason with Allen and Allen reveals that he has more in another location. Soon Thragg starts to succeed in talking him down, but the Guardians of the Globe arrive and Oliver takes the single canister Allen brought and heads towards the planet. Invincible follows and after the two struggle it ends up releasing on Invincible. Invincible asks if it will affect the planet and Allen tells him it was just him that was exposed and that he needs to enter a quarantine away from any other human or Vultrumite.