The people of Vagon Brei had died from a mysterious sleeping sickness that affected both humans and wildlife on the planet. SG-1 and a medical team also fell victim to the illness, which they determined was due to a parasite that triggers the body's production of serotonin and melatonin, causing the individual to fall into a deep coma-like sleep state. On a planet devoid of animal life, a lizard-like creature was discovered in the cave near the village, and Teal'c managed to capture the creature, believing it to have a natural immunity. Once back on Earth, samples taken from the lizard, in conjunction with the research that Carter and Dr. Reimer had completed on the planet, enabled Dr. Lam and her team to synthesize a serum that effectively isolated the parasite and starved it out. With this antidote, the members of SG-1 were able to make a full recovery.
Cross Reference: Bernard Ackerman, Dr. Grimsby, Dr. Reimer, Sleeping Sickness, Vagon Brei, Vagon Brei Parasite
Episode Reference: Morpheus