Written in the 5th century BC, Hippocrates' Corpus Hippocraticum contains 7 books, titled Epidemics (3
). Hippocrates used the adjective epidemios (on the people) to mean "which circulates or propagates in a country" (4
). This adjective gave rise to the noun in Greek, epidemia
We do not know why Hippocrates chose epidemios to title his books instead of nosos, a well-established term meaning disease. Examining the meaning of the term before, during, and after his time may help us understand his choice. Schematically speaking, epidemios (or epidemeo) was used successively to mean "being at homeland" (Homer), "arriving in a country" or "going back to homeland" (Plato), and later "stranger coming in a city" (Demosthenes). Sophocles (495 BC–406 BC) used the adjective in Oedipus Tyrannos to refer to something (a rumor, noise, fame, or reputation) spreading in a country: εῑμ’ Οἰδιπόδα ἐπὶ τ’αν ἐπίδαμον
’ατιν, "I shall go (to make war) to Oedipus, against his fame which spread (in the country)" (verse 494). Oedipus Tyrannos was written at approximately the same time as Corpus Hippocraticum; consequently, we can infer that during Hippocrates' time, epidemios acquired a dynamic meaning, probably more adapted to describing a group of physical syndromes that circulate and propagate seasonally in a human population (i.e., on the people) than nosos, a term used to describe diseases at the individual level.
How epidemios, meaning "on the people," became adapted to mean "that which circulates or propagates in a country" is a crucial question. This evolution occurred during the second half of the 5th century (450 BC–400 BC), a period of intense activity in Greek literature, particularly with the prolificacy of Sophocles. But while nosos or loimos
were frequently used, epidemios was not. In the Perseus Digital Library (http://www.perseus.tufts.edu
), a database that does not yet include Hippocrates' works, the adjective epidemios was used only 9 times, including 4 times in Homer, in the 489 major referenced Greek texts (≈4.8 millions words, 0.02 occurrences per 10,000 words). Its Doric variants epidamos
were used 3 times. In comparison, nosos (disease) was used 712 times in the Perseus database (1.47 occurrences per 10,000 words). The verb epidemeo was used 144 times, primarily during the 4th century and always meaning "to live in or return to one's own country." This lack of material makes accurately exploring the reasons for the semantic evolution across centuries difficult. In Oedipus Tyrannos, Sophocles qualified the sense of epidemios as it referred to reputation or fame; fame naturally spreads in a country. But Hippocrates described a series of syndromes: καὶ γαρ άλλως το νούσημα ἐπίδημον ἦν, "It is a fact that the disease was propagating in the country" (Epidemics, book I, chapter 3). Although Sophocles used epidemios once in that new sense, Hippocrates established a medical meaning for the term.
In Epidemics, books I and III constitute lists of diseases describing clinical cases. Hippocrates compared these cases and grouped them to generate series of similar cases. He adopted a classification approach, initially seeking clinical similarities between cases, thereby discovering, in addition to the notion of epidemic, the more fundamental concepts of symptom and syndrome. However, Hippocrates believed that prognosis was a major aspect of medicine. This belief led him to consider disease a dynamic process with its own progression, a temporal dimension, that represents a first nosologic evolution: syndromic groupings become diseases. Another of the books written by the physician from Kos—Airs, Waters, and Places—deals with the relationships between diseases and the environment, focusing particularly on the habitat of the patients and the season in which disease occurs. Hippocrates tried to determine the effect of environmental factors on what could be described as the distribution of diseases. He was, thus, more concerned about grouping together winter diseases or autumn diseases or diseases that occurred in a particular place or in persons whose way of life had changed than in identifying a large number of cases of the same disease in winter or autumn, at a particular place, or in association with a particular way of life. For Hippocrates, whose nosologic approach already contained a major element of preoccupation with the environment, the first meaning of epidemic was groups of cases resembling each other clinically and the second meaning was groups of different diseases occurring at the same place or in the same season and sometimes spreading "on the people." Thus, Hippocrates applied the word epidemios to groupings of syndromes or diseases, with reference to atmospheric characteristics, seasons or geography, and sometimes propagation of a given syndrome in the human population.
Semantic confusion caused the great Emile Littré, who translated Hippocrates' works into French in the first half of the 19th century, to make a nosologic error. Hippocrates described what is known today, since the work of Littré, as the Cough of Perinthus. This account can be found in Epidemics book VI. Hippocrates described coughs that started toward the winter solstice and were accompanied by many symptoms: sore throat, leg paralysis, peripneumonia, problems with night vision, voice problems, difficulty swallowing, difficulty breathing, and aches. When Littré published his translation and commentaries on Epidemics in 1846, he mistakenly considered the Cough of Perinthus to be a single disease (5
). This error made retrospectively diagnosing the diseases of Perinthus difficult, if not impossible. Moreover, as Littré saw this collection of illnesses as a single disease, he essentially turned it into an epidemic, probably because he had the modern sense of the term in mind and thought that Hippocrates had observed and described an epidemic illness unknown to modern medicine (5
According to Grmek, "Littré took chapter VI, 7.1 as a general description of an epidemic in the sense of this word in the medical language of the 19th century rather than in the sense intrinsic to the works of Hippocrates. In the Corpus Hippocraticum, the noun ‘epidemic' designates a collection of diseases observed at a given place, during a given period. A disease described as epidemic, such as epidemic cough, is a condition occurring from time to time in a given place, the appearance of which is closely linked to changes in season and climatic variations from year to year" (5
Historians of medicine and philologists have over the years attributed the Cough of Perinthus to diphtheria, influenza, epidemic encephalitis, dengue fever, acute poliomyelitis, and many other diseases. However, a French physician named Chamseru, who practiced in the 18th century, almost a century before Littré, finally got to the bottom of what may be meant by the Cough of Perinthus, probably because the term epidemic had not yet taken on the meaning it had in Littré's time. According to Chamseru, the Cough of Perinthus could have encompassed several diseases, among them diphtheria, influenza, and whooping cough (5