The biotech assault that launched in the last issue was a force that accelerates cancerous growth in those exposed. It slowly and surely ate through most staff on the helicarrier, until Stark risked himself by removing the armour and allowing the attacker to try to penetrate his Extremis-filled self. The theory worked, and the Extremis defeated the cancer. Still, Stark can't help but feel he was manipulated into this exact position by an unknown entity.