I've met a backpacking couple who never filter. They fill their water bag from any deep source (lake or river) by swimming out, diving deep and filling the bag there. Because they believe most organisms live in the top few inches. Worked for them; a decade of backpacking all over the world.
On the other hand, one of our Scout leaders got giardia at Boundary Waters, due to incorrect filtration habits. So the article claiming no correlation exists may be an exaggeration.
On the other hand, one of our Scout leaders got giardia at Boundary Waters, due to incorrect filtration habits. So the article claiming no correlation exists may be an exaggeration.