Alexandre Yersin

Because of his immense contribution to the field of public health, he is fondly and affectionately remembered by the people of Vietnam as ‘Ông Năm’.

Yersin was born on September 22, 1863 in Aubonne, Canton of Vaud, Switzerland. His family originally belonged to France. His father, also named Alexandre Yersin, was a teacher of natural sciences in Aubonne and Morges. Unfortunately, he passed away two weeks before the birth of his son.

As a child, Yersin was interested in nature and gathered various tiny organisms like insects that he studied carefully. He grew up in Morges and received his secondary education in Lausanne, before entering the university there.

He later attended the University of Marburg and the Paris Faculty of Medicine in the late 1980s. There he worked in Professor André Victor Cornil's laboratory at the Hôtel-Dieu.

He met fellow bacteriologist Pierre-Paul-Émile Roux by accident. While performing an autopsy on a dead rabies patient, he incidentally cut himself. It was Roux who saved his life by injecting a new therapeutic serum.

In 1886, upon an invitation by Roux, he joined the Louis Pasteur's research laboratory of École Normale Supérieure. Soon after, he joined Roux in the development of the anti-rabies serum.

In 1888, he received his PhD degree submitting a thesis titled ‘Étudesur le Développement du Tubercule Expérimental’ following which he spent a couple of months with Heinrich Hermann Robert Koch in Berlin and continued his studies on the tubercle bacillus. He also obtained French nationality the same year.

In 1889, together with Roux, he isolated a toxin secreted by the diphtheria bacillus (bacterium) and revealed that the toxin, and not the microorganism, was the main cause of the disease.

In 1890, he served as a physician aboard steamships operating off the coast of French Indochina. This marked the beginning of his four-year exploration of the central region of Southeast Asia.

In 1894, he discovered the pathogen that causes plague. It is now known as ‘Yersinia pestis’ in his honor. Through this ground-breaking discovery, he demonstrated that the same bacillus was present in both rodents and humans, leading to the identification of the probable carrier of the disease.