Abstract
Epidemiology can be considered as a very old science. For example, John Graunt, a statistician, published Natural and Political Observations. In the Bills of Mortality in 1662, he analyzed the mortality rolls in London before the Great Plague, presented one of the first life tables, and reported time trends for many diseases. He provided statistical evidence for many theories on disease, and challenged some common beliefs about them. Later, a Greek physician Hippocrates was the first person known to have examined the relationships between the disease occurrence and environmental influences. He believed that the cure to the sickness was to remove or add the humor in question to balance the body; he also mentioned the terms endemic (for diseases usually found in some places but not in others) and epidemic (for diseases seen sometimes but not always). Epidemiology could also be considered as a modern science. Dr. John Snow is indeed famous for his investigations about the causes of the 19th century cholera epidemics in London, and is also known as the father of (modern) epidemiology.