Girolamo Fracastoro (1483-1553), Italian physicist, botanist, astronomer, mathematician and poet. Fracastoro proposed an early theory of the germ origin of disease. His major work, 'De Contagione' (1546), gave the first logical explanation of the long-known facts that some diseases can be passed from person to person or by infected objects. He proposed that infection is due to tiny self-multiplying bodies. Not widely accepted at the time, his ideas were vindicated by Louis Pasteur and others in the 19th century.