Scientists Louis Pasteur, Robert Koch, and Paul Ehrlich all contribute key concepts that form the basis for germ theory, which is a set of ideas that were initially published in 1861 and confirmed via a public health experiment in 1881. The anthrax bacteria, when given in a weakened form to sheep, builds their immunity to it. These scientists prove that microbes cause decay and disease, rather than being a result of these processes as previously thought. This will radically transform the field of epidemiology.