Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics, specific antivirals are used for specific viruses. Antiviral drugs are one class of antimicrobials, a larger group which also includes antibiotics, anti-fungal and anti-parasitic drugs. They are relatively harmless to the host, and therefore can be used to treat infections. They should be distingushed from viricides, which actively deactivate virus particles outside the body.