2 micron is pretty large, might work okay for mountain streams for Giardia,
but wouldn't catch smaller stuff, certainly not viruses. I only know of one water
bottle type that both filters and uses iodine and charcoal that will get both
viruses and bacteria as well as some heavy metals etc. they are from (sp)
Katadin and run around $40. They are handy if you aren't able to get bottled
water, but are a bit heavy and can get you questioned at takeoff because the
tsa folks aren't familar with them. Good to take the documentation if you fly.