Read TFA which addresses this point in several respects. From my skimming of the article: 1. Viruses are believed to have had a beneficial effect (or an effec

Read TFA which addresses this point in several respects. From my skimming of the article: 1. Viruses are believed to have had a beneficial effect (or an effect of some kind) on human evolution. 2. Viruses are mainly bacteriophages and it's possible that "good" viruses keep some bacterial populations in check, but no studies have thus far found this in human beings, although it appears to be true of seawater. 3. The antiviral in question is broken up by the body in a few days, so any increase in bacterial populations that might result from the antiviral would probably be short-lived.