Assuming you were serious with that comment... I highly doubt it. The hippopotamus can't hold a candle to many disease-carrying animals. For example, the mosquito. They're far more widespread, multiply at an extremely fast rate, and some of the diseases they carry have a very high fatality rate(add in the fact much of the world lacks the ability to combat diseases that it may be carrying, and you have one of the true human killers of the animal kingdom). I'm not saying the mosquito kills the most people per year, I'm just saying disease-carrying animals are the obvious "winners"(think the Black Plague).
Having said that, hippopotamuses are very territorial. You only need take a boat across the wrong part of a river. *snap* Your boat, and perhaps you, have been snapped in half.
