"We can survive bacteria, viruses and parasites and wounds"
So can most animals otherwise the most complex life would still be a sponge. And to use my dog as an example again - he can happily drink water from streams and puddles that would put me on the toilet for 2 days.
If you drank water from the puddles and streams often you would probably not end up on the toilet. Don't the people in Mexico (or other countries where they tell tourists not to drink the water) drink the water just fine?