Yer·sin \yer-saⁿ\ (audio pronunciation) Alexandre–Émile–John (1863–1943),
French bacteriologist. Yersin studied bacteriology under Émile Roux in Paris and Robert Koch in Berlin. Later, in Hong Kong, he and Kitasato Shibasaburo independently discovered the plague bacillus at about the same time. In 1944 the genus Yersinia
containing the plague bacillus (Y. pestis
) was named after Yersin.