I know people are focusing on the spread of disease, but I was kind of getting a vibe that the water may be an issue. There were a few times the show was directly involved with water...including the opening scene with Rick dipping into a water barrel. The animals drink water also and Patrick (after getting sick) died in the shower with a lingering shot on the water coming to a slow drip.
All the rotting walkers around there would be a breeding ground for other diseases. As the children in the prison spend time around the fence naming walkers, how many of them have been exposed like Patrick. Who I may add was working at the food counter. Who coughed on the water supply in the showers. Patrick who went out of his way to shake hands with Daryl, who I may point out was eating with and licking his fingers. Did Patrick die from some disease like swine flu? The pig, the water, and the walker at the fence (they kept showing a close up on), the one with bleeding eyes, I think all have a common denominator. ...And at the end when Zach is coughing, its clear Ben hears him but if he is supposedly a medic, or if anything at all (a recovering alcoholic?), he just stays quiet and does nothing, as if he knew what was happening.
Somethings amiss in the prison.