Why did Roomer on Syphon Filter Infected Lian?

In "Syphon Filter: Dark Mirror," Roomer infects Lian with a deadly virus to manipulate her and gain leverage over Gabe Logan. His goal is to use her as a pawn in a larger scheme involving the game's antagonists, exploiting her connection to Gabe. This act highlights the lengths to which Roomer is willing to go to achieve his objectives and adds personal stakes to the conflict between the characters.