Spoiler: show
If it isn't just a disease that is spreading in the came, I wonder if not everyone is infected like Jenner told Rick. The infected can live with it, but if they pass it on to a non-infected, it kills them? Maybe the infected people were exposed to something in Atlanta, but anyone not from Atlanta was not infected? I guess this is the question to be answered later.

The dude coughing in the water wasn't good either