A minority of multi-stage carbon filters can handle the super-fine level of filtration needed to deal with viruses—but most cannot. Instead, those looking to treat potentially dangerous water normally turn to reverse osmosis and ultraviolet radiation systems. Reverse osmosis (RO) filters apply pressure to a water stream, pushing it through a series of semi-permeable membranes, while ultraviolet UV models purify rather than a filter, destroying/disrupting pathogens at a cellular level.
Over-filtering: a word of caution. Once you enter the realm of reverse osmosis and other industrial-grade mechanisms, water can be filtered for contaminants smaller than a fraction of a micron. While this is good news for removing potential health hazards such as viruses, not all contaminants pose a danger to health.
Pouring a bottle of expensive spring water through an RO filter, for example, would remove most of the beneficial salts and minerals dissolved into the liquid. So, depending on where your water comes from, it’s important to weigh up the pros and cons of high-level filtering.
Read next: Comparing the different types of water filter.