Alexander Yersin (entomologist)

Alexander Émile John Yersin (September 22, 1863 – March 1, 1943) was a Swiss-French physician and bacteriologist. He is best known for the discovery of Yersinia pestis, the bacterium responsible for the bubonic plague, in 1894 during an outbreak in Hong Kong.

Born in Aubonne, Switzerland, Yersin studied medicine at the University of Lausanne and later at the University of Marburg and the University of Paris. He was a student and collaborator of Louis Pasteur at the Pasteur Institute in Paris, participating in research on rabies. In 1888, he obtained French citizenship.

In 1890, Yersin left Europe to work as a ship's doctor for the Messageries Maritimes, a French shipping company, traveling to Southeast Asia. In 1894, he was sent to Hong Kong during a plague outbreak. There, working independently from a Japanese team led by Kitasato Shibasaburō, Yersin isolated the bacterium responsible for the disease. While Kitasato initially claimed to have discovered the pathogen, Yersin's work was more conclusive in establishing its role in the plague's transmission and identifying its characteristics. Yersin demonstrated that the same bacillus was present in both humans and rodents affected by the disease, a crucial finding for understanding the plague's epidemiology.

Following his discovery, Yersin remained in Indochina (present-day Vietnam) for the remainder of his life. He founded a Pasteur Institute in Nha Trang in 1895, where he produced serum against the plague. He also made significant contributions to agriculture, establishing a large rubber plantation and experimenting with various crops, including coffee, tea, and quinine. Yersin's work significantly advanced medical research and agricultural development in Indochina. He was awarded the Legion of Honour for his scientific contributions. He died in Nha Trang in 1943. His name is permanently linked to the bacterium Yersinia pestis.