The foregoing observations show that the pneumonia following measles, which has occurred almost coincidentally with pneumonia accompanying epidemic influenza has reproduced the lesions found with influenzal pneumonia. They indicate that influenza attacking patients with measles has had a part in the production of this pneumonia.
The Transmission of Streptococcus Pneumonia.—The importance of streptococcus as a cause of pneumonia following influenza was recognized during the pandemic of 1889–90. Patients suffering with pneumonia following influenza or measles are susceptible to infection by S. hemolyticus and this streptococcus pneumonia may be transmitted from one patient to another throughout a ward in which patients with pneumonia are assembled. There is no evidence that primary pneumonia caused by S. hemolyticus has prevailed as an epidemic in the army or elsewhere in the absence of preceding infection with influenza or measles.
Our autopsies demonstrate that at least half of all deaths which have occurred at Camp Pike have been caused by hemolytic streptococci which have invaded the lung and entered the blood. It is significant that this mortality had its origin in the first half of the epidemic of influenza at a time when the military and medical organization of the camp was confronted with an unforeseen emergency which overwhelmed all agencies for the care of disease. Curves prepared by referring cases of pneumonia in which autopsy demonstrated the nature of the fatal infection back to the date of the onset of influenza, demonstrate that fatal streptococcus pneumonia was frequently acquired during the early period of the epidemic, the maximum number of cases occurring September 23 and 24 and became gradually less common as a sequela of the influenza which began at a later period. Fatal pneumococcus pneumonia had its origin with increasing frequency at a later period, the maximum incidence following influenza which had its onset September 29 and 30. Overcrowding of influenza patients in infirmaries, ambulances and hospital had an important part in the dissemination of streptococcus pneumonia among influenza patients whose disease might otherwise have pursued a benign course.
The most important factor in the high incidence of streptococcus pneumonia has been the spread of the disease in the hospital wards. On September 24 the base hospital contained 2,789 patients, although it had been planned to care for only 2,009. With the progress of the epidemic the number of admissions increased very rapidly, so that on September 30 the hospital contained 3,587 patients and on October 5, 4,233. After September 24 the milder cases of influenza were treated in barracks. The pressing need of diminishing the overcrowding of the hospital was fully recognized and adjacent barracks were transformed into hospital wards; between October 3 and 6, 1,362 patients were transferred from the hospital to these quarters.
In the main hospital, during the period of overcrowding 20 wards for patients with pneumonia were added to the two which already existed. These hastily organized and overcrowded wards have been attacked by outbreaks of streptococcus pneumonia, which during certain periods have been fatal to more than two-thirds of those who have been admitted with pneumonia, whereas in the two long established wards for pneumonia isolated cases of streptococcus infection, which have appeared, have failed to spread to other patients and pneumococcus pneumonia with few exceptions has been found in those who have died. In one newly established ward 67.5 per cent of those admitted within a period of three days have died, and in all of the 23 autopsies which have been performed, streptococcus pneumonia has been found. In another ward 50 per cent of all who have been admitted during a period of one week have died, and among the autopsies performed on these individuals pneumococcus pneumonia has been found in 6 and streptococcus pneumonia in 14. The sputum of 9 patients in this ward has been examined on admission, and pneumococci, but no streptococci, have been found. All these patients have died, and infection with S. hemolyticus has been found at autopsy in 7.
Transmission of Pneumococcus Pneumonia.—Our study of secondary ward infection has not only shown that patients with pneumococcus pneumonia following influenza are susceptible to infection by S. hemolyticus, but that patients suffering with pneumonia caused by one type of pneumococcus may be infected with another type during the course of the disease or after convalescence has begun, the second infection being acquired from patients in adjacent beds. Pneumonia caused by Type IV has ended in crisis and has been followed by a period of normal temperature; recurrent pneumonia has been fatal and Pneumococcus Type II has been found in the organs at autopsy. Pneumonia caused by Type I has been followed by recurrent pneumonia caused by Pneumococcus II atypical acquired from a patient in the next bed. These secondary pneumococcus infections acquired within the hospital are apparently not uncommon.
Prevention of the Transmission of Pneumonia.—The essential factor in the management of influenza and pneumonia is such isolation of each patient that microorganisms cannot be transmitted from one to another or from attendants or others to patients. This condition may be fulfilled by the separation of patients in rooms or isolated compartments especially constructed for the treatment of pneumonia and by the employment of all possible means to prevent the transmission of infection from one patient to another by physicians, nurses and orderlies. It is desirable to examine attendants to determine if they carry hemolytic streptococci in their mouths and to exclude those who are found to be “carriers.”
Influenza is a self-limited disease which, in the absence of complications implicating the lower respiratory tract, is of relatively mild character. When death occurs as the result of influenza it is with very rare, if any, exceptions referable to pneumonia; we have invariably found pneumonia in those who have died in consequence of influenza. The individual attacked by influenza may carry within his upper respiratory passages pneumococci or hemolytic streptococci capable of invading the bronchi and causing pneumonia, but in most instances the microorganism which produces serious pulmonary complications is derived from others with whom the influenza patient has come into contact. The greatest source of danger to one with influenza is contact with patients who have acquired pneumonia, and this danger is immensely increased when infection with S. hemolyticus makes its appearance among pneumonic patients. Hospital epidemics of streptococcus pneumonia will be prevented when the disease is dreaded as much as puerperal fever or the hospital gangrene of former years, and widespread knowledge of the suppurative pneumonias of influenza will bring a clear recognition of the fatal character of streptococcus infection in patients suffering with pneumococcus pneumonia.
Overcrowding of barracks has been an important factor in the propagation of acute respiratory disease and in the transformation of otherwise trivial influenza into fatal pneumonia. Crowded troop trains have doubtless had a part in disseminating infection among newly assembled recruits. Should these dangers be recognized they may be avoided by appropriate measures which will promote rather than retard those military aims which must be placed foremost in time of war. It may be possible by adequate expenditure to avoid the death of thousands of recruits within one month of their entrance into military service.
A second factor in the increase of death rate from pneumonia is the overcrowding and confusion of hospital facilities in the presence of an epidemic disease. When troops are maintained in camps precautions should be taken to provide effective safeguards against the overcrowding of the base hospital.