How the plague bacillus and its transmission through fleas were discovered: reminiscences from my years at the Pasteur Institute in Paris.

Abstract

At present, there are only occasional cases of human plague reported in the United States. As an example, there were only 14 nonfatal cases of human plague recorded in 1988 and 5 cases in 1990. Each resulted from exposure to wild rodents, carrying the plague bacillus and fleas, in the western United States: Colorado, New Mexico, California, Arizona, and Texas. The affected individuals were treated with antibiotics (usually streptomycin and tetracycline) and recovered. Local, endemic outbreaks of plague have been reported from Uganda, Kenya, and the island of Madagascar. More recently, in outbreaks of plague, bubonic or pneumonic, in limited local epidemics, a total of over 700 patients have been reported from certain areas of India in 1994. This manuscript was prepared in order to describe a few interesting details referring to the initial discovery of the plague bacillus and its mode of transmission from the rat carriers to other rats and to humans. A few centuries ago, plague represented a massive disaster, killing millions of local populations in India, China, IndoChina, Africa, and, particularly, Europe. The cause of this disease was unknown and was attributed to unfavorable constellations of stars, to comets, to the wrath of supernatural powers, and frequently also to poisoning of wells by Jews, or other ethnic groups of people, who paid for this with tortures inflicted on them by the panicked population. The mystery of plague was solved fairly recently. Alexandre Yersin, who discovered the bacillus of plague, died in 1943, during World War II. In June 1940, Yersin was in Paris, attending a Pasteur Institute meeting, and left Lutetia Hotel, where he was staying (and where I was staying also at the same time), barely a few hours before the German armies entered the French capital; in fact, Yersin left Paris for Saigon, by air, only 6 hours before the airport was closed. Paul-Louis Simond, who discovered that plague is transmitted by fleas, was collecting plants, and living quietly in retirement, in Valence (province of Drome, south of Lyon), in France, and he very kindly replied in writing to my letters, which I wrote to him from the Pasteur Institute in 1938, asking him for details of his fundamental discovery. Since my childhood years, I have always been interested in finding out how the great medical discoveries were made and how the epidemics of transmissible diseases were prevented. In my early postdoctoral years, I had the opportunity, shortly before World War II, to spend several years, as a young guest investigator, at the Pasteur Institute in Paris. I was intrigued by an isolated laboratory, located in a separate small building, at 25, rue du Docteur Roux. I was told that the upper floor of this small building has a laboratory dedicated to the problem of plague and that it contains notes and records of Yersin, who recognized that this disease infects predominantly rats, and of Simond. I visited this small laboratory several times and studied the notes of Yersin and