Clinical Features.—The 4 cases of hemolytic streptococcus pneumonia following influenza that occurred in this series resembled in all respects the secondary streptococcus pneumonias of the winter and spring of 1918 and presented no features requiring special comment. The onset resembled that of pneumococcus bronchopneumonia, the disease appearing to develop as a continuation of the preceding influenza. The sputum was profuse and mucopurulent in 3 cases, mucoid and bloody in the other. Two cases ran a severe and rapid course with the development of empyema early in the disease and fatal outcome. The other 2 cases ran only moderately severe courses without developing empyema and recovered by lysis in twenty and fifteen days, respectively, after the onset of influenza. Clinical differentiation between streptococcus and pneumococcus bronchopneumonia following influenza did not seem possible without bacteriologic examination of the sputum except in those cases of the streptococcus group which developed an extensive pleural effusion early in the disease.
The advent of superimposed hemolytic streptococcus infection of the lower respiratory tract during the course of pneumococcus pneumonia following influenza presented no clinical features that made diagnosis certain without bacteriologic examination. The sudden occurrence of a pleural exudate during the course of the disease seemed of particular significance, especially since empyema in the bronchopneumonias following influenza was exceedingly rare in the absence of hemolytic streptococcus infection. Other suggestive symptoms were a chill during the course of the disease, a sudden turn for the worse in cases apparently doing well, or the development of a cherry red cyanosis. None of these features, however, was sufficiently constant or distinctive of streptococcus invasion to be depended upon and when they occurred, were merely indications for further bacteriologic examination.
Bacillus Influenzæ Pneumonia Following Influenza
Bacteriologic evidence that cases of pneumonia following influenza might be due to B. influenzæ alone was very meager in the group of cases studied clinically at Camp Pike; in fact, no convincing evidence was obtained that such cases occurred. In one case B. influenzæ alone was found in the sputum coughed from the deeper air passages, and in another case B. influenzæ with a few colonies of S. viridans was found. Both were cases of bronchopneumonia, mild in character, and recovered promptly. They presented no clinical features by which they could be distinguished from cases of pneumococcus bronchopneumonia.
It has been previously stated that B. influenzæ was found in all early uncomplicated cases of influenza somewhere in the respiratory tract; that it was present together with other organisms, notably pneumococcus in the sputum from cases of purulent bronchitis following influenza; and that it was found in the sputum coughed from the lung in approximately 80 per cent of cases of pneumonia complicating influenza. In 35 cases it was very abundant, often being the predominating organism. In all these cases, however, pneumococci or hemolytic streptococci were also present in considerable numbers at the time of onset of the pneumonia. It is impossible to say merely from the clinical and bacteriologic data under consideration what part B. influenzæ played in the development of the actual pneumonia in these cases. Discussion of this subject is therefore reserved for the section of this report dealing with the pathology and bacteriology of pneumonia following influenza.
Summary
Influenza as observed at Camp Pike presented itself as a highly contagious infectious disease, the principal clinical manifestations of which were, sudden onset with high fever, profound prostration with severe aching pains in the head, back and extremities, erythema of the face, neck and upper chest with injection of the conjunctivæ, and a rapidly progressive attack upon the mucous membranes of the respiratory tract as evidenced by coryza, pharyngitis, tracheitis and bronchitis with their accompanying symptoms. In the majority of cases it ran a short self-limited course, rarely of more than four days’ duration, and was never fatal in the absence of a complicating pneumonia.
Bacteriologic examination in early uncomplicated cases of the disease showed the B. influenzæ of Pfeiffer to be present in all cases, often in predominating numbers. It was found more abundantly present during the acute stage of the disease than during convalescence in uncomplicated cases. No other organisms of significance were encountered by the methods employed.
Purulent bronchitis of varying extent developed in approximately 35 per cent of the cases and often prolonged the course of the illness to a considerable extent. Bacteriologic studies showed that it was invariably associated with a mixed infection of the bronchi with B. influenzæ and other bacteria, in most instances the pneumococcus, and indicated that it should be regarded as a complication rather than as an essential part of influenza. Its clinical features consisted of a mild febrile reaction, frequent cough with the raising of considerable amounts of purulent sputum, and the physical signs of a more or less diffuse bronchitis. It led to a varying degree of bronchiectasis in at least some instances.
Pneumonia complicating influenza presented a very diversified picture and appeared to have only one constant character, namely, that influenza was the predisposing cause. It may be best classified on an etiologic basis since the clinical features to some extent and the pathology to a much greater extent depended upon the infecting bacteria in a given case.