Edwin Jenner toiled night and day trying to understand the nature of the zombie condition. At some point during the outbreak, his wife Candace - the head of the CDC - was bitten and infected. Rather than be terminated right away, she volunteered to let Edwin run tests on her and monitor the progression of her infection. Eventually she turned and Edwin put her down, but not before taking various tissue samples to experiment with. Unfortunately, he made little progress before he ran out of suitable samples to use. By that time, he was the only person left at the CDC as all of his colleagues had either fled or committed suicide.
On Day 64, as Jenner is contemplating suicide, he discovers Rick Grimes and his group of survivors pleading to be let inside. Jenner is hesitant at first but decides to open the gates for these wanderers, offering them food and shelter. Later, everyone dines with Edwin and they bombard him with questions. In answer, he brings the group to the control room and talks about the CDC and how he is the last one alive after the rest of the doctors and staff committed suicide - as Jenner puts it, "opting out...".
From the control room, Jenner shows the Atlanta survivors a video of "Test Subject 19's" brain, which offers a picture of the infection and how it affects a person's brain before, during, and after death. It is later revealed that TS-19 was his wife, Candace, the head of the CDC who was infected and devoted her failing body to research in an attempt to find a cure.
When Dale asks about the countdown timer on the wall, Dr. Jenner replies that it is counting down to when the generators in the basement will run out of fuel, prompting an explosion set to destroy the entire CDC. Jenner then closes the doors in the computer lab. The survivors panic and attempt to flee, but Dr. Jenner seals the exit doors of the control room, reminding them of his words when he let them in ("When I close those doors, they won't open again.") claiming that it was no use anyway since he cannot do anything to open the doors to the outside. This causes outrage from the trapped group. He tries to comfort them, saying that the explosion will be peaceful and virtually instantaneous, and Shane attempts to kill him.
Jenner relents after Rick makes a passionate argument and unlocks the control room doors, allowing the survivors to try and find a way out. Before Rick leaves with the rest of the survivors, Dr. Jenner whispers something inaudible to the audience into his ear. Jacqui is the sole member of the Atlanta group who is left behind with him as the building explodes.
In the episode "TS-19", Dr. Jenner whispers something to Rick before the survivors flee the CDC. His words are only revealed in the Season 2 episode "Beside the Dying Fire". Jenner's last words were "It's in our blood, we're all carriers." This reveals that the zombie plague is not merely carried through bites but something that's already affecting the entire human race, causing even those who die a natural death to come back as undead.