The word "disease," like its counterpart in the word "health," still challenges our definition of it. Commonly one of these terms is said to be the opposite of the other. But such a statement fails to give a definition of either. The discovery of "germs" and their presence along with irregularities in body physiology of animals and man have been consoling but not universally curing now for many years. Unfortunately, however, we have not always established causal connection between the presence of the micoorganisms and the disturbed function in the specific vital area. Contemporaneous association of two phenomena is by no means specific proof of causal connection between them. Whether microbes are the real cause of "disease" is still a doubtful matter in many cases so listed, but not carefully examined for possible fallacious reasoning.
Albrecht, W. A.
"Diseases as Deficiencies Via the Soil,"
Iowa State University Veterinarian: Vol. 12
, Article 7.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol12/iss3/7