I guess I was thinking of the Southwest states and particularly the southern end of the CDT where water source are few and far between and often shared with livestock. So picking out hanta "in the US" was a overstatement.  But, anywhere there are cattle there are rodents and it is not uncommon to find a dead rodent in an open water tank. If that is the water source you have to use ...


The general consensus is that water born viruses are relatively rare in the US and that is why you can generally get by with a filter like the Sawyer Squeeze that is not effective for them.

Boiling water for first aid is an option but it assumes you are carrying a pot, stove, fuel and lighter, you are calm enough to set that up and can wait for it to heat up, boil for 1 to 3 minutes depending on altitude, then cool down enough to use. I don't usually carry a stove on a day hike and might not on an overnight or even a longer trip when even canister stoves a banned due to fire danger. Also boiling water for 1 to 3 minutes takes quite a lot of fuel.

Filters are the best primary option in my view because they are quick, don't use fuel and remove particulates and small creatures making sketchy water palatable as well as safe.

But my point was more that carrying Aquamira in your first aid kit is a good idea. It has a long shelf life, is easy to use, works fairly quickly and it only need add 2oz or less to your base weight. While you could argue it is a "packing your fears" item if you are already carrying a filter, having a convenient backup to a relatively fragile, easily lost or even forgotten water filter and a way to cope with some hopefully unusual circumstances seems worth the extra weight to me.