The article about tuberculosis states that Robert Koch in 1882 was the first person to link a particular microbe to a disease. References indicate that Armauer Hansen demonstrated in 1868 that Mycobacterium leprae was associated with the tissues of leprosy patients. He may not have had Koch’s postulates to prove this linkage, but many credit Hansen as being the first individual to implicate a bacterium as the cause of a human disease.

Valerie Vander Vliet
Lewis University
Romeoville, Ill.

William R. Jacobs Jr. of the Howard Hughes Medical Institute at the Albert Einstein College of Medicine in New York agrees that Hansen made such a demonstration and is properly credited for the work. He adds, however, that Koch “was the first to prove and publish that a bacterium could cause disease by fulfilling three criteria: 1) isolation of bacilli from a diseased patient, 2) purification of bacilli, and 3) administration of bacilli into an animal reproduced the tuberculosis disease .”—D. Christensen