[Name] Rust Lung/Lambency [Source] Gears of War 2 [Symptoms] 
When the Lightmass bomb that killed the multitude of Locust monsters in the first game vaporized the liquid element "Imulsion", the gas seeped into the atmosphere of planet Sera, resulting in 'Rust Lung', a disease that spreads quickly and deadly. However, in Gears of War 3 it is concluded that Imulsion is not just a fuel, it's a parasite, and it began to spread to humans as it had to Locust. In fact, as the subterran Locust tried to escape being turned into infested "Lambent", they had to start the genocide of the surface-occupying humans. The Lambent organism is present to some degree in every human's cells by the events of the game, and 'rust lung' is a sing of approaching transformation into a "former human", or just Former, a zombie-like creature. Locust, however, appear not to lose sentience after transformation, and some of them develop uncanny mutations amidst the heat of battle. All Lambent inherit Imuslion's qualities: glow in the dark and explosive properties. The point of the third game is to deal with the Imulsion's assault on the surface of the planet.