No, not at all. Human-to-human transmission is not a biological component, like a human leg, but a biological process, like movement. There are many different things that go into human-to-human transmission, but it comes down to getting into the body, reproducing, and getting out again. There are many different ways to achieve those things. The flu is spread very differently to HIV, which is spread very differently to malaria, which is very different to Legionnaire’s Disease.

Edit: although to clarify, Legionnaire’s Disease isn’t usually spread human-to-human, and malaria is debatable. Cholera would be been a better example of a waterborne disease that enters through the digestive tract.