In the episode "What Remains", Elisabeth Shannon, Jim Shannon, Malcolm Wallace and Nathaniel Taylor discover an outbreak of a mysterious and fatal virus. It was accidenally created by Dr. Douglas Joslyn at Outpost 3, while he was experimenting with genes. The virus has three stages.
First, the infected experience short term memory loss. Anything from forgetting people, to forgetting events.
The final stage can set in from 36 hours, in which the infected goes through a complete mental breakdown.
It was discovered by Elisabeth that the virus could be cured by the Common Cold when she realised that Jim, who had a cold at the time, had not experienced any symptoms, whilst Malcolm had been, even though they were exposed to the virus at the same time.