Jamie Madrox
In "X-Factor" vol. 3 #10, it was revealed that Singularity Investigations was creating a virus designed to kill mutants. While Jamie Madrox referred to this as the Legacy Virus, it is unclear whether Singularity is actually recreating Stryfe's virus, creating what is to later actually be Stryfe's virus, or merely engineering a new one with a similar purpose.