The scientific study of reason and the spread of disease in a particular community are called as epidemiology and the scientists who are researching in this area are called as Epidemiologists. They compare and make a study of the diseases that are very common to that particular community. Different universities, organizations that may be governmental or transnational and the private organizations appoint epidemiologists to make research or work for education or public fitness. They find out different methods of finding and analyzing the diseases that affect the community. They propose and develop effective guidelines concerning pubic health. Their research work includes different subjects like contagious diseases, wounds, infection outbursts, etc. They mainly emphasize on studying different types of diseases, and other health hazards in order to reduce the public health risks. After a deep study of such disease they can make prophecy with regard to the outburst of that disease and also find a possible way out from that specific sickness by preventing it. They also make findings with regard to the risky nature of that disease. By doing research they may even try to find out better precautionary measures to fight such diseases. Biology, disclosure assessment, bio-statistics and even social science disciplines are some extents of which the Epidemiologists take assistance in their effort. The observations as well as the experiments done by the epidemiologist contain evocative, systematic and experimental categories. Their revision brings out the main relationship of disease with factors like biotic agents, smoking, alcohol, tension, chemical elements, etc. The connection of host, agent and the environment with regard to a particular disease is termed as epidemiologic triad. They also study lifestyle of human beings which includes the diet change and corporate measures and find how such lifestyle affects their health directly or indirectly. As part of their responsibility they make aware the general public to be conscious about their health. The sicknesses like cholera and lung cancer is the outcomes of this epidemiological tools. But revisions and their discoveries with regard to some type of diseases may require re-examination with their cause.