Nicolle, Charles Jules Henri (1866-1936), a French bacteriologist, won the 1928 Nobel Prize in physiology or medicine for his discovery that the disease typhus is transmitted by the body louse.

The son of a physician-professor, Nicolle trained as a doctor at the Rouen school of medicine and at the Pasteur Institute in Paris, where he wrote his doctoral dissertation on a form of venereal disease. After completing his M.D. degree (1893), he taught at the Rouen medical school, where he also directed a bacteriology laboratory. Dissatisfied with his career prospects there, in 1902 he accepted the directorship of the Pasteur Institute at Tunis, the capital of Tunisia, which was then a French protectorate. Since the institute was only in the planning stages, Nicolle was able to guide its development and create a prestigious research center. He remained its director for the rest of his life.

The work for which Nicolle was honored in 1928 originated in an outbreak of typhus in Tunis in 1909. Noting that the disease spread rapidly among the general population and among the laundry personnel of the city hospital, but not among the patients or medical staff, Nicolle developed a hypothesis: the disease was spread by lice, which were removed from the patients' bodies and clothing when they were cleaned upon admission. The experiment he designed to confirm his hypothesis involved infecting chimpanzee blood with typhus, and injecting the infected blood into a macaque monkey. Once the monkey developed typhus, Nicolle placed human body lice from healthy people on the monkey, and then transferred the lice to other uninfected monkeys, which soon developed typhus, too. Once the role of lice in the transmission of typhus was confirmed, when the disease spread among prisoners, soldiers, and civilians during World War I (1914--1918), it was brought under control by imposing hygienic measures suggested by Nicolle's research.

In addition to his work on typhus, his discovery that the carrier of a disease can remain healthy proved useful in epidemiology. Nicolle also studied measles, diphtheria, and tuberculosis, among other diseases.