Epidemic

Epidemic (Gr. epi, 'upon,' and dēmos, 'the people'), a disease which attacks numbers of persons in one place, simultaneously or in succession, and which in addition is observed to travel from place to place, often in the direction of the most frequented line of communication. In early days, before the doctrine of contagion was advanced, it was thought that the cause of all disease, both endemic and epidemic, existed in the atmosphere. Hippocrates, while recognising this conclusion as correct regarding the former class of disease, ascribed the latter to something divine or to some unknown and inexplicable cause. Sydenham, the father of English medicine, took a similar view, believing that epidemic diseases were to be attributed to 'a hidden constitution of the air.' Hence the term so frequently used, even in later days, of 'the epidemic constitution.' No doubt there is some foundation for this, seeing that all the great epidemics of ancient time—notably the famous pestilence of the 14th century known as the Black Death—were preceded or accompanied by violent climatic changes, earthquakes and other geological disturbances. But in our age, with the advance that has been made in medical research, the majority of physicians and scientific men are agreed that there is no necessity to go out of the way to seek for an ill-defined and mysterious cause for epidemics, but that the matter may be fairly attributed to well-ascertained and clearly intelligible influences. Examples of these may be adduced in the effect of poverty and overcrowding upon typhus, and inefficient sanitation in the production of typhoid. That famine has much to do with epidemic disease is generally well recognised, so much so that one particular form—relapsing fever—is commonly known as the famine fever. It must still be admitted that there is room for argument on the subject, and so recently as 1884 Dr Norman Chevers, then president of the Epidemiological Society, at a meeting held in connection with the Health Exhibition, attributed typhus fever to the prevalence rather of what he termed an atmospheric wave than to any effect produced by badly ventilated dwellings, though he admitted that this, like the drinking of impure water in cases of typhoid, might be the exciting cause (Health Exhibition Conferences). Epidemics are transmitted from person to person, it is now all but univers- ally agreed, through the medium of minute living organisms, varying in nature according to the different classes of disease. Among the more famous epidemics may be mentioned the Black Death, already alluded to; the Sweating Sickness, which first made its appearance in England in 1485, and afterwards in this and succeeding years became very conspicuous; and a peculiar form of epidemic affection, characterised by gangrene of the hands and feet, which was variously known to ancient writers as Ignis Sacer, Aranea, Mal des Ardens, and at a later period as St Anthony's Fire. The chief epidemics of the 19th century have been cholera, diphtheria, cerebro-spinal meningitis, yellow fever, and relapsing fever. See ENDEMIC for further information on this subject; also CONTAGION, INFECTION, FEVER, CHOLERA, PLAGUE, SMALLPOX, &c.

EPIDEMIC MENTAL DISEASES.—When we consider how ordinary and normal thoughts and emotions spread from one man to many, and sway multitudes to the same views and actions, it is no longer a mystery that morbid conditions of the mind should become at times no less epidemic than physical diseases. Such, at least, is the fact. A mental disorder may spread from man to man, and may involve whole nations. It depends for its propagation, like an epidemic disease, first upon external circumstances, and secondly, upon the peculiar condition or constitution of the individuals affected. Like the bodily affection, the causes which provoke the insanity and the tendency to be affected may have been in process of development for years. Both attack the weak rather than the strong; both exist for a season, and disappear. In the case of the mental malady, the external influences—those which constitute the moral atmosphere—are ignorance or imperfect knowledge, the power of one mind over another, the influence of language, the diffusion of particular opinions, the tendency to imitate. It is probable, however, that physical causes exercise an important influence in the production of such general mental conditions. In 1842 and 1844 there occurred in Germany and France, among the military, epidemics of meningitis with delirium, or inflammation of the membranes of the brain, when no moral factors were at work, but when diet, temperature, &c. were to blame. But even where the origin cannot be so distinctly traced, the co-operation of external as well as psychical agents may be legitimately predicated. It would accordingly be illogical to limit the production of the Dancing Mania (q.v.), which occasionally, during several centuries, swept over Europe, to the reaction succeeding the dread of the end of the world, which had previously prevailed epidemically. An examination of about a hundred manifestations such as that alluded to, collected from various sources, demonstrates that not merely the intoxication of joy, but the most absurd forms of belief—that dreams, delusions, superstitions, corruptions of language, all instincts and passions, even movements and cries, may assume the form, and, to a certain extent, may follow the laws of epidemic diseases. There are records of a histrionic plague, when crowds conceived themselves players, and traversed the streets, and sank and died, repeating verses, and exhibiting extravagant gesticulations; and of whole communities being stricken with nightmare, which was so general as to be supposed contagious. There have been epidemics of homicidal and suicidal mania. In one age hundreds are found possessed by Satan; in another, larger numbers converted into wolves; and the leaping ague of Forfarshire in the 18th century and outbursts of pyromania in various places remind us that there may be still in the constitution of the human mind, and in the education and the habits of life prevailing, elements capable of realising the catastrophe suggested by Bishop Butler's question: What is to prevent a whole nation becoming mad? The instances of epidemic mental disease recorded in the following table have been selected from a vast number of others, with a view of showing not the frequency or extent of such affections, but the range of the phenomenon through the powers and propensities of our nature.

There appears to be no guarantee that the present and future generations shall be exempted from similar visitations, except in the universal diffusion of knowledge and sound thinking, for it is invariably in the darkness of ignorance or in the twilight of imperfect knowledge that the moral plague comes.

See DISEASES, INSANITY, FLAGELLANTS; Hecker's Epidemics of the Middle Ages (Eng. trans. 1846); Calmeil, De la Folie (Paris, 1845); Ackermann, Ueber die Ursachen epidemischer Krankheiten (1873); Küchenmeister's Ztschr. f. Epidemiologie; Parkin's Epidemiology (1880); and Creighton's History of Epidemics in Britain (1891-94).