It seems quite probable from these results that purulent bronchitis following influenza is, in most cases at least, due to mixed infection of the bronchi and should be looked upon as a complication of influenza. Whether the condition may be caused by infection with B. influenzæ alone is difficult to say. No evidence that it may be caused by B. influenzæ alone was obtained in the cases studied. It is not intended to enter here into a discussion as to whether B. influenzæ should be regarded as a secondary invader or not; the other organisms encountered certainly are. It would seem most probable that purulent bronchitis is caused by the mixed infection of B. influenzæ and various other organisms, commonly the pneumococcus, but that the condition is initiated by the invasion of the bronchi by these other organisms in the presence of a preceding infection with B. influenzæ.
Clinical Features.—Purulent bronchitis following influenza began insidiously without any prominent symptoms to mark its onset. About the third or fourth day of influenza, when recovery from the primary disease might be looked for, the patient would begin to cough more frequently, raising increasing amounts of mucopurulent sputum. This sputum was yellowish green in color, copious in amount, and often somewhat nummular in character, sometimes streaked with blood. These symptoms were accompanied by the appearance of coarse, medium and fine moist râles more or less diffusely scattered throughout the chest and usually most numerous over the lower lobes. The percussion note, breath and voice sounds, and vocal and tactile fremitus remained normal. There was no increase in the respiratory rate or pulse rate, and cyanosis did not develop in the absence of a beginning pneumonia. Many such cases, of course, developed bronchopneumonia; in this event areas showing diminished resonance, suppressed breath sounds, and fine crepitant râles with the “close to the ear” quality would appear, the respiratory rate would become increased and cyanosis would become evident. In those cases of purulent bronchitis not developing pneumonia, a moderate elevation of temperature, rarely above 101° F., and irregular in character usually occurred and persisted for a few days or a week.
Many cases maintained a persistent cough, raising considerable amounts of sputum throughout the period of their convalescence in the hospital, which was often considerably prolonged when this complication of influenza occurred. Although no clinical data are available on such cases over a prolonged period of observation, it seems probable that some of them, at least, had developed some degree of bronchiectasis. This would seem all the more probable, since many cases of pneumonia following influenza showed at autopsy extensive purulent bronchitis with well-developed bronchiectasis. Bronchiectasis will be discussed in greater detail in another section of this report. It is this group of cases with more or less permanent damage to the bronchial tree that makes this type of bronchitis following influenza a serious complication of the disease.
Pneumonia
The opportunity presented for a correlated study of the clinical features, bacteriology, and pathology of pneumonia following influenza throughout the period of the epidemic at Camp Pike from September 6, 1918, to December 15, 1918, made it evident that this pneumonia could be regarded as an entity in only one respect, namely, that influenza was the predisposing cause. Clinically, bacteriologically, and pathologically it presented a very diversified picture ranging all the way from pneumococcus lobar pneumonia to hemolytic streptococcus interstitial and suppurative pneumonia with the picture modified to a varying extent by the preceding or concomitant influenzal infection.
One hundred and eleven consecutive cases in which careful clinical and bacteriologic studies were made form the basis of the material presented. Of these cases, 38 came to necropsy so that ample opportunity was presented to correlate the clinical and bacteriologic studies made during life with the pathology and bacteriology at necropsy. It has seemed advisable to group the cases primarily on an etiologic basis with secondary division according to clinical features in so far as this can be done. Bacteriologic studies showed that at the time of onset these pneumonias were either pneumococcus pneumonias or mixed pneumococcus and influenza bacillus pneumonias in nearly all instances. Certain of these cases later became complicated by a superimposed hemolytic streptococcus or a staphylococcus infection. In a few instances hemolytic streptococcus pneumonia directly followed influenza without an intervening pneumococcus infection. B. influenzæ was present in varying numbers in nearly all cases. In only 2 instances however, was it found unassociated with pneumococci or hemolytic streptococci, once alone and once with S. viridans.
Clinically the cases fell into four main groups: (1) Lobar pneumonia; (2) lobar pneumonia with purulent bronchitis; (3) bronchopneumonia (pneumococcus); (4) bronchopneumonia (streptococcus). It should be borne in mind, however, that the picture was a complex one and that correct clinical interpretation was not always possible, since many cases did not conform sharply to any one type and superimposed infections during the course of the disease often modified the picture.
Pneumococcus Pneumonia Following Influenza.—Bacteriologic examination of selected and washed specimens of sputum coughed from the lungs at time of onset of pneumonia showed the various immunologic types of pneumococcus to be present in 105 cases. The incidence of the different types is shown in Table XIV.
| Table XIV | ||||
|---|---|---|---|---|
| Types of Pneumococcus in 105 Cases of Pneumococcus Pneumonia Following Influenza | ||||
| LOBAR PNEUMONIA | BRONCHOPNEUMONIA | TOTAL | PER CENT | |
| Pneumococcus, Type I | 8 | 0 | 8 | 7.6 |
| Pneumococcus, Type II | 3 | 1 | 4 | 3.8 |
| Pneumococcus, II atyp. | 12 | 7 | 9 | 18.1 |
| Pneumococcus, Type III | 3 | 3 | 6 | 5.7 |
| Pneumococcus, Group IV | 32 | 36 | 68 | 64.8 |
The most noteworthy feature of the figures in Table XIV is the high proportion of pneumonias due to types of pneumococci found in the mouths of normal individuals, 93 cases or 88.6 per cent, being caused by Pneumococcus Types II atypical, III, and IV. This is in harmony with the results generally reported and is in all probability due to the fact that in patients with influenza pneumococci, which under normal conditions would fail to cause pneumonia, readily gain access to the respiratory tract and produce the disease. It is also of interest that with one exception the highly parasitic pneumococci of Types I and II were associated with pneumonias clinically lobar in type.