Though Fracastoro wrote this book more than a century before Leewenhoek invented the microscope, and could only express the theory of contagion in very general terms, this book represents a landmark in the development of ideas that centuries later led to the work of Bassi, Henle, Davaine, Koch, and others. For that reason we have classified Fracastoro as a precursor of foundational theories of infectious disease by microorganisms.
Fracastoro was the first to state the germ theory of infection. He suggested the contagiousness of tuberculosis. Haeser even describes him as the “founder of scientific epidemiology”. This book, which contains one of the first accounts of typhus (pp. 43-44), marks an epoch in the history of medicine, since Fracastorius enunciated in it, perhaps for the first time, the modern doctrine of the specific characters and infectious nature of fevers. He is remembered for his poem on syphilis, but he was also eminent as a physicist, geologist, astronomer, and pathologist. An English translation by W. C. Wright appeared in 1930.