Alexandre YersinBorn 23 Sep 1863; died 1 Mar 1943 at age 79.Swiss-French bacteriologist who co-discovered the plague bacillus, Pasteurella pestis (also called Yersinia pestis and Bacillus pestis). With Pierre Roux he discovered the diphtheria toxin (1889). Yersin discovered the plague bacillus simultaneously with Shibasaburo Kitasato (1894) in Hong Kong, where he had been sent by the French government. The Japanese bacteriologist Kitasato had arrived days earlier and had secured priority to the limited facilities. Nevertheless, Yersin gained a sample of pus excised from a plague victim, and was able almost immediately isolate the plague bacillus. Yersin then set out to attenuate the bacillus and develop an anti-plague serum. He successfully treated his first plague patient, a Chinese student, in 1896.