Timothy... are you looking for an everyday home water filter or for emergency use?.. my emergency use system is a 5 gallon (.1 micron absolute filter) bucket system from Sawyer.... they have a .02 micron system for virus...the filter media is strands similar to blood dialysis membranes, and can be back flushed with a supplied syringe
if you have a lot of sunlight, you might look into the SODIS system using natural UV wavelength from the Sun, in transparent 2L bottles..