Generally, water filters are designed to remove waterborne protozoa and bacteria, but not viruses. If viruses are a threat where you are travelling, your water filter can be used in combination with water purification methods (ie. UV light, chemical treatments or boiling) in order to deactivate viruses. Alternatively, mechanical pump purifiers are now available that can physically remove viruses quickly and easily.
Our range of water filters are designed to remove waterborne protozoa and bacteria. Water filters are considered sufficient when traveling in areas where human traffic is low and protozoa (like cryptosporidium and giardia), and bacteria (like E. coli and salmonella) are considered the main threats. In order to remove bacteria and protozoa, backcountry-grade microfilters must remove contaminants down to 0.2 microns.
Viruses are far smaller than protozoa or bacteria so can slip through the technologies of backpacking filters. Traditionally, UV light, chemical treatments or boiling were required to deactivate viruses by scrambling their DNA or killing them. New advancements in mechanical pump purifiers, however now provide options to physically remove viruses quickly and easily.
If you are traveling to less-developed countries, where water treatment and sanitation infrastructure is poor and/or people don't practice good hygiene near water supplies, a water purifier (which removes or deactivates viruses) is considered the best option. Any waterborne viruses that are harmful to humans are transferred primarily through human waste. Therefore, where there are less humans, we assume the risk of viruses is also lower. Common viruses to be aware of include norovirus and hepatitis A. To combat these, a microfilter plus a purifying agent, like chemical tablets, is also a robust option.
It is important to remember that while chemical treatments, UV light and boiling will deactivate the microorganisms, they won't rid the water of particles. Particles in the water can impede the effectiveness of UV light and to a lesser degree, chemicals.