>>64164540
Iodine is plenty effective against bacterial and viral pathogens, even in relatively heavily contaminated water. Just extend the treatment time and up the concentration if you're especially concerned, prefiltering through a bandanna or filter papers will help too.

Where iodine falls down is against cryptosporidium and that's likely to be a concern in many serious emergencies. You'll need a proper filter (Sawyer mini works) for that, but it won't do shit against viruses.
Boiling works against everything so long as you have time for a fire. Pic rel too.