In 1894, Kitasato Shibasaburo isolated the causative bacillus from buboes, later named Yersinia pestis, while he researched the plague at the request of the Japanese government. Concurrently, Alexandre Yersin, a member of the French Colonial Health Service in Hong Kong isolated from buboes the causative bacillus that later was named Yersinia pestis in his honour.

In 1890, Kitasato and Emil von Behring, announced the discovery of diphtheria antitoxin serum. Both, Kitasato and Von Behring were nominated for the 1901 Nobel Prize, but only Von Behring was awarded the honor.