Epidemic Respiratory Disease / The pneumonias and other infections of the repiratory tract accompanying influenza and measles

by Eugene L. Opie; Francis G. Blake; Thomas M. Rivers; James C. Small

Pneumococcus pneumonia uncomplicated by streptococcus infection (shown by area with single hatch in chart) pursued a course which more closely conformed to the curve representing influenza. The cases of influenza which resulted fatally bore a fairly constant ratio to the total number of cases of influenza from the onset of the epidemic until October 1, but subsequently few cases of influenza developed fatal pneumococcus pneumonia.

These charts arranged with reference to the onset of fatal pneumonias dissociate very clearly the outbreak of streptococcus pneumonia, which reached its height at the beginning of the influenza epidemic, from the uncomplicated pneumococcus pneumonia which reached its maximum at the midpart of the influenza epidemic and then abruptly abated.

Chart 1—Showing the relation of (a) onset of cases of pneumonia shown by autopsy to be uncomplicated by secondary infection with hemolytic streptococcus, indicated by upper continuous line with single hatch, and of (b) onset of fatal cases of streptococcus pneumonia, indicated by the lower continuous line with double hatch, to (c) the occurrence of influenza, indicated by the broken line. The onset of each case of fatal pneumonia is represented by a single square.

Our study of ward infection in pneumonia furnishes an explanation of the outbreak of fatal streptococcus pneumonia coincident with the initial stage of the influenza epidemic. This outbreak is a true epidemic of streptococcus infection superimposed, in many instances at least, upon preexisting pneumococcus pneumonia, but in some instances, doubtless, a primary streptococcus pneumonia, following the bronchitis of influenza. In the absence of secondary streptococcus infection a very large proportion of these individuals would have recovered. This epidemic of streptococcus pneumonia, it has been shown, was the result of unfavorable conditions produced by great overcrowding of the hospital and in the early part of the epidemic by inadequate separation of those with streptococcus infection from those with none. With control of these conditions, streptococcus pneumonia rapidly diminished.

Greater susceptibility to pneumococcus pneumonia in the early than in the late period of the epidemic is perhaps explained by differences in the severity of influenza; the more susceptible individuals were attacked by influenza in the early period, whereas the less susceptible did not acquire the disease until they had been exposed to an immensely increased number of infected individuals. A better explanation is furnished by the greater opportunity at the beginning of the epidemic for the transmission of microorganisms causing pneumonia, for at this time patients with influenza were crowded together and methods to prevent the transmission of infection were little used.

Bronchitis

Clinical study has shown that purulent bronchitis (see Fig. 2) occurs in about one-third of the cases of influenza. In a large proportion of cases of bronchitis there is no clinical evidence of pneumonia. The bronchial lesions found in association with the pneumonia of influenza are an index of the ability of the agent, which causes influenza, to injure the bronchi.

In those who have died with pneumonia following influenza the large bronchi (with cartilage) are intensely injected, so that the mucosa has a deep red color which on cross section contrasts very sharply with the pearly white of the cartilage. Superficial injury to the bronchi is not infrequently evident in the larger bronchial branches; superficial loss of epithelium is indicated by erosion of the surface, whereas somewhat deeper destructive changes are occasionally evident. Microscopic examination accurately determines the degree of destructive change.

Purulent bronchitis was noted in 134 autopsies (55.6 per cent of autopsies). From the small bronchi, in many instances, purulent fluid welled up upon the cut surface of the lung, whereas in other instances tenacious mucopurulent fluid could be squeezed from small, cut bronchi by pressure upon lung tissue. The consistency of the material within the bronchi varied greatly, ranging from a viscid and tenacious mucus of creamy, yellow color to a thin, turbid, gray fluid. The coexistence of local inflammatory or of general edema of the lungs modifies the character of the material found in the bronchi at autopsy; with edema the purulent exudate is in some instances diluted so that a thin cloudy fluid flows from the small bronchi. In the presence of advanced edema of the lungs the bronchi rarely if ever contain purulent exudate. The underlying changes in the bronchi are more significant than the character of the exudate found at autopsy. Nevertheless, the group of cases in which the diagnosis of purulent bronchitis has been made, because small and medium sized bronchi have contained purulent or mucopurulent exudate, represents instances of readily recognizable bronchitis of considerable severity.