Alexandre Yersin

Early life and training

Yersin was born at Aubonne in the canton of Vaud on 22 September 1863, the youngest of three children^[1][3]. His father, also named Alexandre (1825 to 1863), was superintendent of gunpowder for French-speaking Switzerland and a teacher of natural sciences at Aubonne and Morges; he died of a cerebral haemorrhage shortly before his son was born^[1]. His mother, Fanny-Isaline-Emilie Moschell, raised the three children at Morges, where she ran a school for girls^[1].

He studied medicine at Lausanne from 1883 to 1884, then at Marburg and at the Hôtel-Dieu in Paris from 1884 to 1886^[1]. In 1886 he joined Louis Pasteur's laboratory at the École normale supérieure at the invitation of Émile Roux and worked on the rabies serum^[1]. He took his doctorate in 1888 with a thesis on the development of experimental tubercle, spent two months with Robert Koch in Germany, and obtained French nationality that year so that he could practise in France^[1].

In 1889 he joined the newly founded Pasteur Institute as Roux's collaborator. Together they showed that Corynebacterium diphtheriae releases a soluble toxin that produces the effects of diphtheria, the first bacterial toxin identified^[1].

The plague bacillus

From 1890 to 1894 Yersin served as a ship's doctor for Messageries Maritimes, first on the Saigon to Manila line and then on the Saigon to Haiphong line, and took part in one of the Pavie missions^[1]. Plague broke out severely in Hong Kong in May 1894 and threatened every port trading with China, Haiphong among them^[2].

The French government sent Yersin to Hong Kong on 5 June 1894^[1]. He reached the city on 15 June, working without the support given to the Japanese bacteriologist Kitasato Shibasaburō, who had arrived three days earlier^[1][2]. Yersin obtained material from the bodies of plague victims, found Gram-negative bacilli in the buboes, reproduced the disease in animals and sealed a specimen in a glass tube that was sent at once to Paris^[1].

The dates given for the discovery differ. The Vietnamese Wikipedia article and part of the English article record that Yersin announced the finding on 20 June 1894^[1][2]; another passage in the English article dates the discovery to 23 June 1894^[1]. The result was communicated to the French Academy of Sciences the same year in the paper La peste bubonique à Hong-Kong^[1]. The organism was called Bacterium pestis, then Bacillus pestis from 1900 and Pasteurella pestis from 1923, before taking the name Yersinia pestis about 1970^[1].

Nha Trang and the Pasteur Institute

Yersin left the shipping company in 1891 and chose to live at Nha Trang, where he had a wooden house built at Xóm Cồn and opened a clinic^[2]. In 1895 he returned to the Pasteur Institute in Paris and, with Émile Roux, Albert Calmette and Borrel, prepared the first anti-plague serum; in the same year he went back to Indochina and set up a small laboratory at Nha Trang to make it^[1][2]. That laboratory became a branch of the Pasteur Institute in 1905^[1].

He tested the serum at Canton and Amoy in 1896 and at Bombay in 1897^[1][2]. Canton and Guangzhou are the same city under two names, and the two sources characterise the 1896 trial there differently: English Wikipedia reports disappointing results from those campaigns^[1], while Vietnamese Wikipedia records that Yersin was allowed to inject a seminarian with serum prepared at Nha Trang and obtained a rapid result^[2]. He returned to Nha Trang in 1898 after Bombay^[2].

Exploration, farming and cinchona

On the instruction of the Governor-General Jean-Marie de Lanessan, Yersin led an overland expedition from Biên Hòa by way of Đồng Nai and Di Linh and reached the Lâm Viên plateau; his diary of 21 June 1893 records villages of the D'Lat people there^[2]. In 1899 Governor-General Paul Doumer established a hill station for Europeans on the ground Yersin had described, and it became Đà Lạt^[2].

In 1896 he founded the stock farm at Suối Dầu, breeding horses for serum production, and he later bought about 500 hectares at Suối Giao, now Suối Dầu, for farming and stock^[2]. He was the first to bring rubber trees into cultivation in Vietnam and ran a plantation of about 100 hectares, the income of which supported his institute^[1][2].

From Suối Giao, after a short expedition with Armand Krempf that took two days by boat and two days of climbing, he reached the mountain of Hòn Bà^[2]. He used prize money from scientific awards to build a winding road 30 kilometres long from Suối Giao up to Hòn Bà, and in 1915 he moved plants and animals there and sowed seed^[1][2]. At Hòn Bà he acclimatised the cinchona tree brought from the Andes, the source of quinine against malaria, and the trees allowed Indochina to meet its own quinine needs during the Second World War^[1]. He also introduced cacao and coffee^[1].

Hanoi and later positions

In 1902 Governor-General Paul Doumer, before leaving Indochina, called Yersin from Nha Trang to Hanoi to open a medical school, a hospital and a hygiene centre^[2]. Yersin was accredited as the first head of the Hanoi medical school on 8 January 1902^[1].

He was awarded the Leconte Prize in 1927 and was named honorary director of the Pasteur Institute and a member of its board of administration in 1934^[1].

Death, tomb and memory

Yersin died of myocarditis at his house in Nha Trang on 1 March 1943^[1][2]. His will directed that he be buried at Suối Dầu^[2]. Wikidata carries both 1 March and 28 February 1943 as the date of death, the first with two references and the second with one^[3].

The tomb stands on a low hill inside the Suối Dầu stock farm of the Pasteur Institute of Nha Trang, in Suối Dầu commune about 20 km from the city^[2][4]. OpenStreetMap places it at latitude 12.1790 and longitude 109.0683^[5]. In 2020 the province recovered more than 3.65 hectares there, covering the whole of the national relic site, and transferred the land to the provincial heritage centre^[4].

Streets named after Yersin kept their names after 1975, his house in Nha Trang holds the Yersin museum, and the village of Tân Xương in Suối Dầu worships him as a tutelary spirit^[1][2]. The people of Xóm Cồn called him Ông Năm or Thầy Năm; the English Wikipedia article attributes the name to the five stripes of his colonel's insignia, and the biographer Patrick Deville to the five gilt stripes on the white uniform he wore as a ship's doctor^[1][2].