So Jenner's conclusions from 12 months back regarding the virus meant that no other scientist in the world was also doing research on the virus at the same time or after Jenner's passing?
In addition, Jenner never said that there was no cure for the virus. In fact, he specifcally stated that the French was closest to finding a cure before communication was lost. The fact that Glenn was at the CDC makes it more likely for me that he bought Eugene's BS because he was aware that there existed scientists who were working on a possible cure.
I am sure 500 gallons of drinking water is going be useful for Glenn, Tara, Maggie, Abe and Rosita when they are dead after being suprised by a horde of walkers.
After their run in with the Termites, I wouldn't be surprised if the group was more concerned about humans than zombies when entering an apparently deserted building. I'd probably take my chances with predictable zombies than alert any humans potentially lurking in the bookstore by knocking on the door or loudly announcing your arrival.