Antibiotics only fight bacterial infections. Flu -- whether it’s typical seasonal flu or swine flu -- is not caused by bacteria, but by a virus. So antibiotics have absolutely no effect on any kind of flu.

There are instances of flu complications that involve bacterial infection.  The flu virus can weaken your body and allow bacterial invaders to infect you.  Secondary bacterial infections to the flu include bronchitis, ear infections, sinusitis, and most often, pneumonia.