It is apples and fish... the question was about leptospirosis, which is a bacteria, and responders started talking about protozoa and viruses, which are managed entirely differently.

I agree that thoroughness is essential in many parts of the world anymore. Just a filter, or just chemical treatment might not be enough for many water sources. If you learn what you might encounter and know your enemy you can be prepared with the right treatment instead of a mixed bag you aren't sure will work.

MNS