[repsilat]

If the infected cells tend to live a long time and the antiviral drug kills them all at once then it's a big difference. To see this, take the idea "to the limit":

Imagine if virus-infected cells lived an average of ten years, that the antiviral drug kills every infected cell in the body instantly, and that every cell in the body is infected. The effect of taking the drug in such an instance would be far worse than letting the virus attack the body unchecked.

Now, this obviously isn't a "reasonable" example, but it does show that there are parameters for which there the drug does harm the patient. Determining whether that risk is actually worth worrying about is a job for science.

[aidenn0]

Ah, but infected cells are hijacked to do the virus' job rather than the job they are intended for so any killed cells weren't aiding the body.