Do gravity filters remove viruses?

Most backpacking gravity filters in this group use roughly 0.1-micron hollow-fiber media that removes bacteria and protozoa but not viruses, which is generally adequate for North American backcountry water. Countertop systems with finer ultra-filtration or proprietary elements claim broader reduction, but verify the specific NSF/ANSI or IAPMO certification listed for the model you're considering.