The factors that determine the rise, spread, and degree of severity of epidemic diseases / M. Greenwood.

  • Greenwood, Major, 1880-1949.
Date:
1913
Catalogue details

Licence: In copyright

Credit: The factors that determine the rise, spread, and degree of severity of epidemic diseases / M. Greenwood. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    of secular or long-period modification in virtue of which a specific type becomes dominant in a particular epoch and then gradually or suddenly gives place to a rival. (2) There is another set of factors producing short- period oscillations in the epidemicity of a given disease leading to the phenomena of seasonal prevalence. But, finally, we can connect these two trains of ideas by the conception of an epidemic constitution in virtue of which certain types of epidemic or certain features of morbidity tend to prevail at a given time to the exclusion of other types or other symp- toms. We may say that the amplitude of the first kind of wave is measured in centuries, that of the second in months, and that of the last in years. This analysis is, of course, imperfect, particularly in its attempt to characterize so intricate an idea as that embodied in the doctrine of epidemic constitutions, but the antithesis between the secular and ephemeral aspects of epidemic disease does, I think, correspond to realities worthy of our close attention. Just as the student of geology must com- bine a knowledge of the changes now proceeding in the crust of the earth with an investigation of those effected in past time to make a complete science, the epidemiologist cannot hope to grasp the whole truth if he concentrates his attention upon contemporary or recent phenomena. One should, I think, endeavour to follow the vicissitudes of some definite disease through a considerable period of time in order to realize the existence of secular factors, and then separately investigate the immediate features of various epidemics. These two lines of study are not, indeed, absolutely distinct, yet little is lost and something gained in respect of clearness if we agree so to regard them for the purposes of description. I propose to follow this order in my subsequent remarks, and hope to have made it seem probable that such a course is in accord with the views of our greatest English epidemiologist. The first branch of the inquiry can be most conveniently illustrated by the case of plague, but as this is a subject which my colleague, Professor Dr. Sticker, can treat with far greater knowledge than I, it will be better to confine myself to epitomizing the history of scarlet fever, a less satisfac- tory but still instructive example. (c) Secular Changes in Epidemicity as illustrated by Scarlet Fever That scarlet fever prevailed in ancient times is a proposition we can neither prove nor disprove, and although we shall probably agree with Haeser (iii. 69) that some proportion of the disease termed morbilli by the translators of the Arabian physicians may have been scarlet fever, it is equally impossible to reach any satisfactory conclusion as to its preva- lence or fatality in mediaeval times. 1 his is particularly tantalizing since were morbilli to any extent identifiable with scarlet fever the latter may have been more fatal than small-pox in the Middle Ages.1 1 Schnitzlein argued that scarlet fever was known to Rhazes, and Willan also contended for its antiquity. A careful discussion will be found in Richter’s paper.