I remember in season 4 of The Walking Dead that Glenn, Sasha and a few others were infected with some type of illness and that they were still sick even when the Governor attacked them. How were they healed? I remember Hershel was helping them out before he got beheaded. Was that what finally helped them to overcome the illness?
During Season 4 Episode 3- Isolation Daryl, Tyreese, Michonne and Bob leave the prison to find some antibiotics at a veterinary college that Hershel knew about, they find the antibiotics in Episode 4- Indifference and return to the prison in Episode 5- Internment at which point Hershel and Bob begin to distribute it among the infected.
After they left in Isolation, Hershel had also left the prison with Carl to find some Elderberries which he made into tea, a natural remedy for the flu as they knew it would take a while for them to get to the clinic due to the large distance and walkers.