Under fever symptoms we shall refer only to the variations of body temperature. With the initial chill the body temperature rapidly rises. Only in a few cases has the temperature been taken at the time of the chill, and it has then been found, as in several of our hospital cases (especially doctors and nurses), to be 40° C. or higher. This initial rise of temperature is, in mild cases, often the highest during the whole course of the disease. A rapid rise of temperature is the rule, but in some cases the temperature rises gradually, the acme being reached on the second or third clay. The duration of the fever is generally that of the attack; in simple influenza, from one to several days. Frequently, however, the fever disappears before the other symptoms of influenza, and, indeed, not uncommonly there is a great disproportion between the height of the fever and the intensity of the other symptoms-a further proof that the nervous symptoms and the general phenomena of influenza are not dependent upon the rise of temperature.
Should the fever be protracted, the curve may have one of several forms. Like Kormann, we have noted a type of high continued fever (39° to 40° C.) lasting several days, and terminating either rapidly or gradually. More frequently it is of a remittent or intermittent type, with the ordinary morning remissions, or of the typus inversus, or quite irregular.
The temperature, even in simple cases, usually reaches 39° C. at some time during the course of the disease; generally it rises even higher. Temperatures of 40.5° or even of 41° C. (0. Frentzel), even in uncomplicated cases, lasting but one, two, or three days, have been observed, although a moderate degree of fever is the general rule in simple cases.
It is possible that an afebrile course, as noted by many authors, may occur in very rudimentary and abortive cases. Eichhorst states that "afebrile cases of influenza are not at all uncommon, and they are especially characterized by severe nervous symptoms." Without doubt in such seemingly afebrile cases the transitory initial rise has remained unrecorded because the temperature was not taken at the time. It is certainly not proper without further data to class as afebrile those cases which began with decided chilliness or rigors, even though during the time that they were under observation by the physician they had no fever.
So called hyperpyrexia! temperatures (41.5° to 41° and over) are not at all uncommon for a short time in simple influenza,* but they are more frequent with certain complications.
These marked hyperpyrexial temperatures have been noted especially in the rare cases where influenza sets in with severe cerebral symptoms, loss of consciousness, coma, hemiplegia (encephalitis grip palis), and soon terminates fatally.
Defervescence may be either rapid, especially in cases lasting only one or two days, or gradual, with steadily diminishing diurnal excursions.
A phenomenon, to whose frequency I can testify, considered by Teissier and others to be almost pathognomonic, is a fall of temperature for one or two days, while the other influenza symptoms continue, this being followed by a recurrence of the fever lasting from one to several days, generally with an increase of all the other symptoms of the disease. Krehl says: "Frequently several days of normal temperature are interposed between these febrile periods." This may be called a bileptic or polyleptic influenza. Thus we have a marked tendency to relapse indicated already in the course of the attack of influenza, caused, no doubt, by a cumulative production of pyogenic or other toxins, which are then absorbed and enter the circulation.
* "Child, nine months old; sudden onset of the influenza with severe convulsions. Two hours later temperature in the rectum 41.3° C. Mild course." (My influenza lectures, p. 25.) The German army report mentions a case of influenza pneumonia with a temperature of 41.5° C. intra vitam and of 43° C. (?) five minutes after death.
We must mention here an important but rare form of the fever, which has been frequently emphasized in literature and is well known to us.* We refer to the cases of protracted pyrexia in uncomplicated influenza in which the fever shows a regular quotidian intermittent type. Since in such cases, during the intermission, the other influenza symptoms are also less prominent (euphoria), and the rise in temperature is always sudden and often accompanied by a rigor, while the defervescence is accompanied by sweating, the picture of such an influenza attack closely resembles an intermittent quotidian ' fever. It is probably such cases which have given rise, in times past and present, to the erroneous view that influenza was a modified malaria . We would explain these cases as resulting from a periodic activity of the influenza bacilli in the formation of their pyogenic products.
Lastly, there are those rare, diagnostically deceptive cases in which the disease, after a typical onset, lasts for two or three weeks, with high continued fever (39° to 40° C), but without any respiratory or other complications, and occasionally with but slight development of nervous symptoms. The temperature chart resembles that of enteric fever, but all the other signs, namely, the sudden onset with rigor, the general appearance of the patient, the absence of cerebral symptoms, of the dry tongue, of meteorism, of roseola, and of diarrhea, exclude even the possibility of an abnormal attack of enteric fever. In these cases influenza appears as a protracted febrile affection without any localizing symptoms (Hagenbach).
This is the protracted form of the pure influenza fever, due, apparently, to a continuous formation of pyogenic products by the specific bacteria. That there is no definite proportion between the production of the pyogenic and the neurotoxic poisons appears obvious from the disproportion between the febrile and the nervous symptoms.
In the following description of the symptomatology of influenza we shall consider the separate organs in detail. It will not be possible to mention all the immense literature in this field, and we shall have to limit ourselves, even as regards those writers who have assisted in building up the clinical pathology of influenza.
* Influenza lectures, p. 25, Kornblum, loc. cit.