Sigma Virus

The Sigma Virus (シグマウィルス) is a Maverick Virus from the Mega Man X series that turns Reploids into Mavericks.

Brief story
Zero was the first Reploid to hold this virus (It's speculated that Wily created this virus, by analyzing the Evil Energy.), but it technically doesn't turn him in a Maverick, as he was already created with a evil personality by Dr. Wily.

Several years after his creation, Zero is found by the Maverick Hunter Sigma, which fights against Zero and a part of this virus passed to him, merging with his DNA and becoming later the "Sigma Virus", Sigma himself becoming a virus. After being repaired by the Maverick Hunters, Zero had no memories of his evil self and became good. Through, Zero was unaware that he holds this virus (weakened after the fight against Sigma), and scattered it throughout the world during his missions as a Maverick Hunter.

In Mega Man X5, Zero notices he is immune to the Sigma Virus, which makes him stronger instead of affecting him. Sigma spread the Sigma Virus through the world to make Zero absorb a large quantity of it, to reactivate Zero's original self dormant inside him.

As Sigma's DNA merged with the virus, and it later returned to Zero's body, Gate was able to revive Sigma by analyzing a piece of Zero's DNA, but it was not a perfect copy. After acknowledging he was the original carrier of the virus, Zero allowed himself to be sealed (shown in his ending of Mega Man X6) to be studied by a research facility to create a cure to the virus, leading to the end of the virus and the Maverick Wars years later.

Mega Man X2
In Mega Man X2, the Sigma Virus is the final boss, a 3D wire frame head of Sigma.

Mega Man X3
In Mega Man X3, Sigma attempts to possess X's body after being defeated, as the bodies he created where not strong enough to defeat him, but the vaccine created by Dr. Doppler weakened him and X escaped.



Mega Man X5
In Mega Man X5, Sigma spreads the Sigma Virus through the world, and it appear as a enemy that looks like a purple Sigma head. If X gets hit with it several times, he will get a condition that damages him for a while. If Zero gets it, he actually becomes stronger (mainly because he is the original bearer of the virus).

Zero Virus
Zero Virus (ゼロウィルス) is a powerful virus re-created by Sigma by combining the Sigma Virus and the virus in the space colony Eurasia.

It is the original form of the Sigma Virus, that was carried by Zero before it infected Sigma. In Mega Man X5, it appears as a enemy in the final stages, a purple virus that looks like Zero.

