To add to what msscamp said... there is a time when antibiotics are used when combatting a virus, and it's for the purpose of preventing secondary bacterial infections that may appear due to the weakened immune system. The antibiotics are never for the purpose of fighting a virus, because they won't do a lick of good.
Supportive care... an example would be if you have a calf with scours caused by a virus, supportive therapy can include probiotics, IV/SQ fluids, electrolytes, pain meds, vitamins/minerals (with caution), that sort of thing.