Many diseases have high mortality rates. The true answer depends upon the geographic location you are concerned with. In many underdeveloped countries infectious gastroenteritis due to water born or food born microorganisms cause a very high death rate. In more developed countries diseases like cancer, heart disease, and diabetes have very high death rates. In the United States cardiovascular disease has always ranked high on the list of culprits. Some authorities attribute this fact to our nutrition and lifestyle habits.