It is perhaps well, first to define exactly what is meant by secondary contact infection in influenza and pneumonia. In our experience at Camp Pike it was found that a very large percentage of the pneumonias following influenza were accompanied by secondary infection with pneumococcus, some few being caused by hemolytic streptococcus. The types of pneumococcus encountered were almost entirely those that are found normally in the mouths of healthy men, approximately 85 per cent being Types II atypical, III, and IV. It has been generally accepted that infection with these types of pneumococci is usually autogenous—that is, that under the proper conditions of lowered resistance an individual becomes infected with the pneumococcus that he carries in his own mouth. Many observations made during the course of the present work have suggested that this is probably not so in many instances and that the influenza patient may not be so much in danger from the pneumococcus that he normally carries in his own mouth as he is from that carried by his neighbor, in other words, he is in danger from contact infection. The same considerations hold true with respect to hemolytic streptococcus infection. Secondary contact infection in cases of already existing pneumonia following influenza were found to occur frequently. These were for the most part caused by hemolytic streptococcus infection superimposed upon a pneumococcus pneumonia. Many instances of double pneumococcus infection, however, either coincident with or following one another were encountered.
Secondary Infection with S. Hemolyticus in Pneumonia
Pneumonia caused by streptococci was repeatedly observed[[50]] during the pandemic of influenza which occurred in 1889–90. With clearer recognition of the characters which distinguish varieties of streptococci several observers have shown that secondary infection with hemolytic streptococci may occur during the course of pneumonia and though definite evidence has been lacking have suggested that it may be acquired within hospital wards. That a similar secondary infection with S. hemolyticus in pneumococcus pneumonias following influenza occurred not infrequently at Camp Pike during the epidemic was shown by bacteriologic studies made during life and at autopsy in a considerable series of cases. During the early days of the epidemic of influenza, secondary streptococcus infection was almost entirely limited to certain wards which were opened for the care of the rapidly increasing number of patients with pneumonia. During this period these wards were overcrowded, organization was incomplete, and the opportunities for transfer of infection from patient to patient were almost unlimited. The spread of streptococcus contagion and its fatal effect may be clearly brought out by comparison of these wards with wards that had long been organized for the care of patients with pneumonia.
Ward 3 had been in use for the care of patients with pneumonia for some time prior to the outbreak of influenza. It was provided with sheet cubicles and conducted by medical officers, nurses and enlisted men accustomed to the care of patients with pneumonia, ordinary precautions being taken against transfer of infection from one patient to another. The data in Table XVII show the average number of patients in the ward, the number of new cases of pneumonia admitted, and the number of deaths among patients admitted during the corresponding period, for three periods of ten days each from September 6 to October 5. The types of infection in fatal cases as determined by cultures taken at autopsy are also shown.
| Table XVII | |||||||
|---|---|---|---|---|---|---|---|
| Pneumonia in Ward 3 | |||||||
| AVERAGE NUMBER OF PATIENTS IN WARD | NUMBER OF PATIENTS ADMITTED | TOTAL DEATHS AMONG PATIENTS ADMITTED DURING THE CORRESPONDING PERIOD | CULTURES AT AUTOPSY | ||||
| NUMBER | PER CENT | PNEUMOCOCCUS | S. HEMOLYTICUS | UNDETERMINED (NO AUTOPSY) | |||
| Sept. 6–15 | 18.6 | 11 | 3 | 27.2 | 3 | 0 | 0 |
| Sept. 16–25 | 46.1 | 52 | 16 | 30.7 | 13 | 1 | 2 |
| Sept. 26–Oct. 5 | 58.6 | 23 | 8 | 34.7 | 5 | 1 | 2 |
During the period from September 6 to 15, just prior to the outbreak of influenza in epidemic proportions, the ward had an average population of 18.6 patients. The total number of new patients admitted was 11, of whom 3 died, a mortality of 27.2 per cent. All these cases were pneumococcus pneumonias as determined by bacteriologic examination of the sputum at time of admission. The 3 fatal cases showed pneumococcus infection at autopsy. During the second period, from September 16 to 25, with the outbreak of the epidemic of influenza, the ward rapidly filled with new cases of pneumonia, attaining an average population of 46.1 patients. Of the 52 new cases admitted 16 died, a mortality of 30.7 per cent. Again all the cases admitted during this period in which bacteriologic examination of the sputum was made, were found to be pneumococcus pneumonias with one exception. This case, admitted on September 21 and dying two days later, had a hemolytic streptococcus pneumonia. Fortunately, though quite by accident, he was placed in a bed at one end of the porch and no transmission of streptococcus infection to other cases in the ward took place. At autopsy 13 cases showed pneumococcus infection; the foregoing case, hemolytic streptococcus. During the third period from September 26 to October 5 the ward became even more crowded, having an average of 58.6 patients; 23 new cases were admitted, 8 of whom died, a mortality of 34.7 per cent. Autopsy showed that 5 of these were pneumococcus pneumonias and 1 was caused by hemolytic streptococcus infection. It is noteworthy that the death rate from pneumonia gradually increased as the ward became more and more crowded. This may possibly be attributed in part to the increasing severity of the pneumonia during the early days of the influenza epidemic. That it was in part directly due to secondary contact infection with pneumococcus will be shown when the transmission of pneumococcus infection is discussed. In spite of the overcrowding of the ward the introduction of 2 cases of streptococcus pneumonia did not cause an outbreak of streptococcus infection. Whether this was due to precautions taken against the transfer of infection or was merely a matter of good luck is difficult to say, in view of the fact that a considerable amount of transfer of pneumococcus infection from one patient to another did occur.
Ward 8 had long been used for the care of colored patients with pneumonia. As in Ward 3 cubicles were in use and ordinary precautions against the transfer of infection were used. The data are presented in Table XVIII.
| Table XVIII | |||||||
|---|---|---|---|---|---|---|---|
| Pneumonia in Ward 8 | |||||||
| AVERAGE NUMBER OF PATIENTS IN WARD | NUMBER OF PATIENTS ADMITTED | TOTAL DEATHS AMONG PATIENTS ADMITTED DURING THE CORRESPONDING PERIOD | CULTURES AT AUTOPSY | ||||
| NUMBER | PER CENT | PNEUMOCOCCUS | S. HEMOLYTICUS | UNDETERMINED (NO AUTOPSY) | |||
| Sept. | |||||||
| 6–20 | 25.5 | 18 | 2 | 11.1 | 2 | 0 | 0 |
| Sept. 21–Oct. 5 | 46.1 | 59 | 20 | 33.9 | 10 | 1 | 9 |
During the period from September 6 to 20, prior to the outbreak of influenza in epidemic proportions among the colored troops, the ward had an average population of 25.5 patients; 18 new cases of pneumonia were admitted during this period, all of whom were pneumococcus pneumonias as determined by bacteriologic examination of the sputum at time of admission to the ward. Only 2 died, a mortality of 11.1 per cent, autopsy cultures showing pneumococcus in both cases. All these patients were treated on the porch of the ward while they were acutely sick. During the second period from September 21 to October 5, when the influenza epidemic was at its height, the ward rapidly filled with active cases of pneumonia and became distinctly crowded. It contained an average of 46.1 patients, but had actually reached a population of 64 patients at the end of the period. Of the 59 new cases admitted, 20 died, a mortality of 33.9 per cent, 10 with pneumococcus pneumonia, one with hemolytic streptococcus pneumonia. In 9 there was no autopsy. The conditions in Ward 8 were quite analogous to those in Ward 3. In spite of the overcrowding during the second period no outbreak of secondary infection with S. hemolyticus occurred, but secondary pneumococcus infection did occur as will be shown below.
In contrast with these two wards are Wards 1 and 2 in which widespread secondary contact infection with S. hemolyticus took place. Ward 2 was opened September 26, at the beginning of the period when 20 new wards for pneumonia were organized. From September 26 to October 1 the cubicle system was not in use, the ward was crowded, organization was imperfect, and few precautions were taken to prevent transfer of infection from one patient to another. On October 2 the cubicle system was installed and precautions against transfer of infection were instituted. The data are shown in Table XIX.