There is cold in the head, more severe in most cases than ordinary simple coryza. The eyelids are swollen and reddened, there is lachrymation, sneezing is frequent, and the discharge from the nose is abundant. Epistaxis is not rare. Sore throat, with tickling sensations and difficulty in swallowing, is due to inflammation of the pharynx and neighboring parts. In many instances the catarrhal symptoms are due to a pharyngitis and tonsillitis only, the lower air-passages escaping. Hoarseness is common.
Cough is a prominent symptom. It is apt to be frequent and distressing—sometimes paroxysmal from the beginning of the sickness, almost always so at some period of its course. Its spasmodic character in some of the older epidemics led to the confounding of epidemic catarrhal fever with whooping cough. It is apt to be worse toward evening and at night, but the sick are often tormented day and night by the loud racking cough. It often leads to vomiting, and by its violence and persistence gives rise to pain and soreness in the muscles of respiration (myalgia), and occasionally to hernia. It is at first dry or attended with a scanty muco-serous expectoration; later on the sputa become opaque and muco-purulent, and in consumptive or full-blooded persons or those having mitral disease they are sometimes streaked or mingled with blood. Toward the close of the attack the cough becomes less urgent and loses its spasmodic character. In some epidemics cough is not a prominent symptom, and a few cases are encountered in most epidemics in which well-developed influenza runs its course without unusual, peculiar, or excessive cough. If the cough be due to bronchitis, we find on auscultation the physical signs of that affection. They are of course wanting when it is due simply to laryngo-tracheal irritation. Hence we frequently detect sonorous and sibillant or mucous and subcrepitant râles upon both sides of the chest in the course of the attack, as in non-epidemic acute bronchitis; and, on the other hand, cases occur where the auscultatory signs are but little or not at all altered from those of health. It is scarcely necessary to add that there are no special physical signs that can be regarded as diagnostic of influenza.
Many patients suffer from dyspnoea. Although due in some instances to complications, it occurs with remarkable frequency in those in whom none of the objective signs of any pulmonary lesion can be discovered. It is here of nervous origin. Graves assumes a direct disturbance in the function of the vagus as its cause. This view is sustained by the observation that the dyspnoea is now and then intermittent, or shows rhythmically recurring remissions, which are unattended by alteration of the physical signs. To Biermer it appears more probable that the congestions so common in influenza, not attended by marked physical signs until they lead to oedema, are to be regarded as the cause of the dyspnoea. It varies greatly in intensity. In many patients it goes on to marked oppression, great shortness of breath, precordial pain, and the like. In certain epidemics orthopnoea and suffocative attacks were very common. Stitches in the side and pain under the sternum are observed without appreciable physical signs.
Symptoms Referable to the Nervous System.—Great prostration of muscular strength is a very early symptom, and constitutes, in most epidemics, one of the remarkable features of the disease. Patients from the onset feel extremely weak, and are exhausted by the slightest bodily effort. The ordinary strength is not regained until convalescence is far advanced.
Headache is a constant symptom. Severe frontal pains are scarcely ever absent. They extend across the brow and deeply about the orbits and at the root of the nose, having their seat in the Schneiderian mucous membrane and its prolongations lining the frontal sinuses and the nasal ducts. Sometimes the pain is referred also to the region of the antrum of Highmore and to the Eustachian tube and the middle ear. It occasionally extends over the whole head. Cutaneous hyperæsthesia of the head and neck and stiffness of the neck-muscles are also met with. The headache is often most intense; it lasts commonly till the end of the attack, and may even outlast it. It increases in severity with the fever and mental agitation toward evening. The occurrence of epistaxis affords some relief.
Among the more constant symptoms of influenza are very severe pains in the limbs. Patients experience sensations of soreness and bruising, such as follow the most severe and unaccustomed muscular effort. Dull, tearing, and burning pains are felt sometimes in particular muscles or tendons; sometimes they are diffused over the whole body. Distressing pains of a dragging or boring character in the loins and calves of the legs are complained of. These pains are neither relieved nor aggravated by gentle movement or by moderate pressure. A sense of contraction of the chest and precordial distress also occurs, and stitches in the side (pleurodynia), substernal pain, and pains in the throat and nape of the neck are common. When the attack is severe the patient is usually restless, sleepless, and anxious. Dizziness and a tendency to faint occur on rising, particularly in women. Mild delirium is not uncommon, but the more intense forms are occasionally observed. Active delirium was thought to be a mortal symptom in some of the older epidemics.
The inability to sleep bears no direct relation to the intensity of the fever. It is seen in some cases where fever is slight or even absent.
Somnolent states also occur. Great hebetude and torpor have marked some epidemics. That of 1712 was called the sleepy sickness, by reason of the prevalence of these symptoms.
In grave cases painful muscle-cramps, subsultus tendinum, twitchings of particular muscles, and tremblings of the hands occur.
The mental power is enfeebled, and the acuteness of the special senses is diminished.