Are there waterborne viral infections other than polio and hepatitis A? If not, it seems reasonable to rely on vaccines and not worry about viruses when choosing a hydration method/system.

Most first-worlders are already covered for polio and many are wise to get covered for hepatitis A (and B).

Am I missing something?

> Are there waterborne viral infections
Only about 10 million of them. And no, I am not really exaggerating.

Not all of them will kill you by any means, but many will make you very sick. For a basic example, look up the general rotavirus family. Now realize it is but one of MANY.

Cheers