Rustlung is a disease first described early on in Gears of War 2 by Tai Kaliso to Dominic and Marcus. The disease apparently started to affect humans shortly after the Lightmass Bomb was deployed. It is said to not be contagious, but Tai Kaliso makes it a point to let Dom and Marcus know that the hospital they were in, and in fact the rooms they were passing through housed patients being treated for Rustlung. Tai further explains that although told that the disease was not communicable, he stayed away as a precaution. This disease may be cause by the breathing of air from imulsion fumes. This is said when Dom and Marcus are on a Locust Gunship going through multiple imulsion fumes in Act 3. and when Dom gets to close to a dead imulsion-infected drone in Act 4. Also, a sympton of Rustlung also seems to be coughing up brown chunks from one's lungs, as evident in Jonathan Harper's Prisoner Journal, which can be found in the prisoner camps.