I never said anything about anti-virals. Hershel said it wasn't the virus that was killing, but the secondary infection, which is why he said they need antibiotics.
I actually think he said the symptoms are more killing people, which makes sense. When your body is suffering from an illness it tends to get stupid and tries to kill the disease by killing the patient. Take running a fever as an example, you run a fever in order to raise the body temperature in hopes of killing the invaders that way. Well, too high of a fever can kill you, so we have medications to keep high fevers under control.
Coughing, sneezing, running noise all ways the body copes with trying to get invaders out of the body and all things that can kill in extreme circumstances. So the goal seems to be whatever they can do to curb the symptoms is the goal right now under the hopes that the body will eventually cope with disease.
It is a problem they're looking for antibiotics which are useless against viruses.