- The Male Infected Host Mask,
- The Female Infected Host Mask,
- The Male Infected Virus Mask, and
- The Female Infected Virus Mask.
They were first released as a reward for completing the Daily Quarantine Event, and were released as Halloween items during the 10-28-09 Patch.
Each mask had its own statistics, depending on whether it was a Host mask or a Virus Mask. These included Speed, Protection, and Protection from Gas boosts.
From 9/29/10 to 10/5/10, everyday if you played 5 matches of Seize and Secure, you got a free 1-Day Infected Mask.