Antibiotics are meant to kill living things (bacteria). Viruses, on the other hand, we are not sure if they would classify as living. Viruses change the meaning of "life" if we consider them alive. They can only reproduce within another cell by taking over that cell. An antibiotic would have to be able to kill human cells to kill a virus, and that would not be a good medicine to take. Viruses invade a host cell and incorporate the virus DNA into the host cell's DNA, which would cause the host cell to create more viruses to invade other cells.