A system of practical medicine. By American authors. Vol. 1

by Unknown

Many of the older observers speak of the intermittent character of influenza in certain epidemics, and its tendency to run into intermittents, particularly of a certain type, during convalescence. This has not been observed in the outbreaks of later years, and it is probable that in such instances an endemic malaria has modified the epidemic catarrhal fever, or the former has broken out as the latter passed away.

Pregnant women are in danger of aborting.

PATHOLOGY.—Our knowledge of the pathology of influenza is as yet very imperfect. Biermer has described it as the sum of a series of catarrhal manifestations developed under a common epidemic influence. The close association of the various local affections arises from their almost simultaneous occurrence as results of primary pathological processes common to them all. Each of the three groups of symptoms which make up the clinical picture of the disease—namely, the fever, the catarrh, and the symptoms referable to the nervous system—constitutes a distinct factor of influenza, and is a direct outcome of the action of the infecting principle. There is no constant interdependence among these groups, either in the order of their succession or in their intensity. Thus, while all three groups are commonly present from the beginning of the attack, any one of them may be the first to appear or have an intensity out of all proportion to each of the others. The fever is not a result of the catarrhal inflammation, nor are the nervous symptoms the result of both the others. They all spring directly from the action of the same cause.

This view is at variance with the opinion—based upon the fact that ordinary acute local inflammatory diseases, tonsillitis, bronchitis, and the like, sometimes run their course in a similar way to influenza, with fever, nervous depression, and a serious sense of illness—that influenza is a simple epidemic catarrhal inflammation.

The sudden onset of influenza, its not infrequent abrupt termination, which suggests crisis, its unsparing seizure of great numbers of the population, the severity of the nervous symptoms, and the amount of laryngo-bronchial irritation, often out of measure with the lesions of the mucous membranes,—all point to the action of a morbid agent affecting the body at large. The severity of the symptoms also, in many cases, is much greater than in similar acute non-specific local affections, while the complications, and in particular the recrudescence of fading neuralgias and the tendency to abortion, and the sequels, as cough, weakness, headaches, flying pains, which often remain long after convalescence, are evidences of its belonging to the group of infectious diseases rather than to that of simple acute inflammatory diseases.

In conclusion, it must be urged that the similarity of the symptoms in many epidemics, occurring during the course of several centuries and under different social conditions, and even different degrees of civilization, forcibly demonstrates the specific and definite character of the causes which give rise to influenza.

Very little light is thrown upon the pathology of the disease by the anatomical changes found after death. Uncomplicated influenza is rarely fatal. As a rule, the unfavorable termination is due to lung complications. The essential lesions are congestion and catarrhal swelling of the mucous membrane of the upper air-passages and the bronchial tubes. These changes may be restricted, in the lungs, to the trachea and larger bronchi, or they may extend to the finest twigs. They may amount to great thickening and deep capillary injections of the mucous lining of the tubes, which contain clear, frothy mucus or thick, viscid masses of muco-purulent secretion unmixed with air.

More or less congestion of the gastric mucous membrane, and more rarely of that of the intestine, is also met with. The solitary and agminate glands of the intestine are not affected, save as the result of special complications. A few observations relate to the finding of enlarged and softened bronchial glands. More extended researches are needed, not only upon this point, but also in the whole domain of the pathological anatomy of the disease.

Hyperæmia, oedema, hypostatic congestions, splenization, catarrhal pneumonia, and hepatization affect the lung-tissue in cases fatal by the complications which are associated with such changes. The tissue-changes of diseases existing prior to the attack of influenza, such as old consolidations, tubercle, brown induration, emphysema, and so forth, are of course frequently discovered.

DIAGNOSIS.—The discrimination of influenza from other affections having some points of resemblance to it is, under ordinary circumstances, unattended with difficulty. The march of the epidemic, the number of persons attacked, the prominence of the nervous symptoms, the rapidly developed debility, and the character of the cough, usually severe out of proportion to the physical signs, distinguish it from all other epidemic diseases.