Not sure which MSR guide you mean, but this one agrees with my recollection: https://www.msrgear.com/blog/water-treatment-101-cryptosporidium/ https://www.msrg

Not sure which MSR guide you mean, but this one agrees with my recollection: https://www.msrgear.com/blog/water-treatment-101-cryptosporidium/ https://www.msrgear.com/blog/water-treatment-101-cryptospori... Cryptosporidium is relatively easy to remove by filtration, and not so easy to kill with chlorine. Even chlorine dioxide seems to kill cryptosporidium rather slowly: https://www.outdoorgearlab.com/reviews/camping-and-hiking/backpacking-water-filter/aquamira-water-treatment-drops https://www.outdoorgearlab.com/reviews/camping-and-hiking/ba...