Infected people are permanently put into hazmat suits that can inflate to size & gas masks that release gas/helium. You still think & talk normally, but you're muffled, due to the hazmat suit's mask. Known as an "Inflatable Hazard", because victims getting put into hazmat suits are theorized to be "hazardous" & other silly theories made. There's other people in hazmat suits too, but they're not all bad people, wanting to help you get used to being in the suit, and get along with other victims.