Fracastoro’s De contagione et contagiosis morbis et eorum curatione, in which he postulates that diseases are caused by the spread of “seeds” or “seminaria” that could self-multiply, is generally considered to be the first work to attribute disease to unseen “germs” and helped lay a foundation for modern understanding of infectious disease.

Girolamo Fracastoro epitomized the Renaissance thinker. He studied medicine at Padua and became a physician, but he was also a poet, philosopher, a natural historian who developed theories of fossils, and, like his contemporary at Padua Nicolaus Copernicus, an astronomer. He produced a work in 1538 in which he suggested that the Earth and planets traveled in spherical orbits around a fixed point, foreshadowing the later work of his contemporary, Copernicus. In the same treatise, Fracastoro discussed superimposing lenses—one of the first descriptions of a telescope. He also observed that all comet tails point away from the Sun, a fact that later was determined to be related to the solar wind. Medicine;Italy
Fracastoro, Girolamo
Paul III
Fracastoro, Girolamo

Religious communities often tended to the sick, injured, and dying in public rooms, or wards, such as the one depicted here (sixteenth century Paris), where diseases often spread easily and rapidly.

(Frederick Ungar Publishing Co.)

Medicine, however, is the field in which Fracastoro’s contributions are most noted. In the early 1500’, after the return of Spanish explorers from the New World, Europe was experiencing a new, virulent infectious disease. Now known as syphilis, Syphilis;Europe this disease derives its name from a 1,300-verse poem, Syphilis sive morbus Gallicus (Syphilis: Or, A Poetical History of the French Disease
Syphilis (Fracastoro) , 1686; better known as Syphilis), published by Fracastoro under his Latin name, Hieronymous Fracastorius. This poetic work gives a mythical account of a shepherd, Syphilis, who angers Apollo and is cursed with the disease. In this poem, Fracastoro first articulates his thoughts on contagion and the spread of disease.

Fracastoro argues that nature is complex but understandable through careful study. He suggests that syphilis did not have a single point of origin followed by spread, and he suggests natural causes for the disease. He also suggests that the particles that cause the disease can be carried by air and that they can remain dormant for years before “breaking out.”

Fracastoro continued his observations about infectious disease and his studies of syphilis, and in 1546 he published a treatise on infectious diseases, De contagionibus et contagiosis morbis et eorum curatione
De contagione et contagiosis morbis et eorum curatione (Fracastoro) (1546; De contagione et contagiosis morbis et eorum curatione, 1930), in which he is the first person to use the word “contagion.” Fracastoro defines contagion as an infection passing from one person to another. He accurately describes the three stages of syphilis: the small genital sore (primary syphilis), lesions and a body rash several months after the initial sore (secondary syphilis), and dementia (caused by brain deterioration) and other organ destruction (tertiary syphilis). He also describes the mode of transmission of syphilis, noting that it is a sexually transmitted disease, and he recognizes the fact that a woman infected with syphilis can pass the disease to her child during pregnancy or after birth through her breast milk.

Fracastoro described the causative agents of syphilis as “seeds” or “seminaria.” Since the first microorganisms were not seen until the 1670’s and 1680’s by Antoni van Leeuwenhoek (1632-1723) and others, it is unlikely that Fracastoro envisioned the seminaria as the microorganisms described by those scientists. However, Fracastoro did propose three modes of transmission of seminaria between individuals. In the 1546 treatise, he states that diseases could be transmitted by direct contact, indirectly by contact with infected objects such as dirty linens, or across a distance by contaminated air.

Fracastoro was able to apply his theories to practical situations. When plague broke out in Verona, Fracastoro left for Lake Garda. There he practiced medicine from his country house and served as physician to Pope Paul III. After the Treaty of Crespi (1544) ended the wars between the Holy Roman Emperor Charles V (r. 1519-1558) and the French king Francis I (r. 1515-1547), Pope Paul III convened the Council of Trent (1545-1563) Trent, Council of (1545-1563) . The purpose of the council was to address important questions of Catholic faith and discipline including the canonization of the Scriptures. The council met seven times, but an outbreak of the plague disrupted the work of the council. Fracastoro urged that the Council of Trent be moved to Bologna to avoid the contagion of the plague. However, members of the council who supported Charles V refused to leave, and Pope Paul III postponed the meeting indefinitely in April, 1547, to avoid a schism within the Church.

Fracastoro’s description of disease transmission and contagion did not immediately lead to the development of sterile techniques or successful treatments directed at the “seminaria” that he believed caused diseases. In fact, more than three hundred years passed after the 1546 publication of De contagione et contagiosis morbis et eorum curatione before the modern germ theory of disease was developed by Robert Koch (1843-1910). The development of the modern germ theory required several technological and intellectual developments, including the design of the compound microscope, with which Leeuwenhoek first observed microorganisms or, as he called them, animalcules.

Additionally, the theory of “spontaneous generation” of organisms had to be disproved before the science modern bacteriology could develop. This theory held that life could arise spontaneously out of inanimate matter (as appeared to be the case when maggots appeared in dead meat); Leeuwenhoek held that life could arise only from life, and eventually Lazzaro Spallanzani (1729-1799) disproved spontaneous generation through experiments he conducted in 1765.

In the early 1860’, Louis Pasteur (1822-1895) concluded that “diseases of wine” were caused by microorganisms, or “germs.” Shortly after, Joseph Lister (1827-1912) extended Pasteur’s work to show that microorganisms cause infection in wounds, and he developed antiseptic techniques in surgery.

In many ways Leeuwenhoek’s theories culminated in the work of Koch, who in 1876 developed the germ theory of disease in which he identified the bacterium (now known as Bacillus anthraxis) responsible for causing anthrax. In this work, Koch used four steps to prove that the bacterium caused anthrax. He first isolated the bacterium from all of the infected animals, next he grew anthrax bacteria in “pure culture” in the laboratory, then he infected a healthy animal with the cultured bacteria, and finally he re-isolated the same bacteria from the infected test animal after it developed the disease. These same steps are followed by twenty-first century epidemiologists as they search for the causes of emerging diseases.

• Gould, Stephen J. “Syphilis and the Shepherd of Atlantis.” Natural History 109 (2000): 38-48. An article giving historical perspective and context for Fracastoro’s poem “Syphilis and the Shepherd of Atlantis.” Compares Fracastoro’s poetic documentation of syphilis to the less dramatic completion of the genome sequence of Treponema pallidum, the organism that causes syphilis.
• Hudson, Margaret M. “Fracastoro and Syphilis: Five Hundred Years On.” Lancet 348 (1996): 1495-1497. Discusses the spread of syphilis in Europe, Fracastoro’s Syphilis sive morbus Gallicus, and his contributions to Renaissance science.
• Lederberg, Joshua. “Infectious History.” Science 288 (2000): 287-293. Historical discussion of the control and treatment of infectious diseases from the 1400’s to the present day. Includes a time line of infectious diseases.
• Thurston, Alan J. “Of Blood, Inflammation, and Gunshot Wounds: The History of the Control of Sepsis.” Australian and New Zealand Journal of Surgery 70 (2000): 855-861. Describes the contribution of military medicine to the development of control and treatment for wound infections and sepsis.

1517: Fracastoro Develops His Theory of Fossils

Beginning 1519: Smallpox Kills Thousands of Indigenous Americans

1530’s-1540’s: Paracelsus Presents His Theory of Disease

1543: Vesalius Publishes On the Fabric of the Human Body

1546: Fracastoro Discovers That Contagion Spreads Disease

1553: Servetus Describes the Circulatory System