Yellow Fever [antikvár]

AUTHOR'S PREFACE It would seem natural, in writing a history of any disease, first to collect the different accounts of its occurrence and from them to determine its extent and severity in different epochs. From these data would be determined its extension or diminution in area and in intensity -time being our other variant. Ultimately, from the historical facts thus presented, the epidemiology of the disease would, or might, be derived. Thus, indeed, have our existing histories of diseases been written. A different-almost a reversed-method will be followed for yellow fever in this work, and for these reasons: The reports and accounts of the occurrence of yellow fever-and of its absence as well-are, in a number of cases, not only unreliable, but erroneous. This was inevitable. The diagnosis of yellow fever is not always clear, and it was especially apt to be mistaken when yellow fever was considered, on the one hand, to be an intense form of malarial fever, and on the other, typhus fever modified by a hot climate. Both of these diseases have been reported as yellow fever, and yellow fever has been reported certainly as the first, if not as the second. On the other hand, certain facts in the epidemiology of yellow fever are established and definitely known, and by them we can, in many cases, test-in somé test absolutely-the truth or error of the account submitted to us. We know quite well the conditions necessary for the existence of yellow fever, for it to become epidemic and to continue at any place; and when we find its existence or an epidemic reported where the conditions necessary therefor do not exist, we know that the disease reported as such is not yellow fever. Similarly, when yellow fever is reported as continuing for a term of years at a place under conditions where this continuance is impossible, we know either that the disease in question was not yellow fever or that it ceased and was reintroduced. Provided that we are conservative and postulate no conditions except such as are pro ven, there is no escape from these two conclusions; and by them not a few questions which have given rise to much and bittér controversy can be settled definitely and-what is more important- settled correctly.