Stargate Universe Season 2 Episode 4 (Stargate Universe s02e04) with title “Pathogen” aired on Tuesday, October 19th 2010 at 09:00 pm via Syfy Network
Here is summary for Stargate Universe Season 2 Episode 4 :

The crew of the Destiny faces more interplanetary peril. As it continues to grow, Chloe starts to go through some unexplained changes. Eli becomes concerned and the rest of the ship starts to follow his worries as they try to get to the bottom ofChloe’s uncharacteristic confusion. Is it really Chloe or something else?