The first disease whose bacterial cause Robert Koch proved was anthrax. In 1876, while working in Wollstein, Koch demonstrated that the bacterium Bacillus anthracis caused anthrax in livestock and humans.
Anthrax was a particularly revealing subject because the organism could form durable spores. Those spores survived harsh conditions and later germinated when conditions became favorable, helping explain how the disease could reappear in fields and spread among animals. Koch isolated the organism, followed its development, and linked it consistently with the disease.
This achievement helped establish the principle that a particular microorganism could cause a particular disease. It was a foundation for modern medical bacteriology and strongly supported the developing germ theory. Koch’s later work on tuberculosis and cholera made him even more famous, but anthrax came first.
Readers sometimes choose tuberculosis because Koch is closely associated with identifying its bacterium in 1882. Tuberculosis was a later milestone; anthrax was the earlier breakthrough that launched Koch’s reputation.