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Thomas Francis, Jr., M. D.
Influenza as a Military Problem
The long history of influenza does not indicate a close association between its epidemic occurrences and major military undertakings. Because of the frequency of both phenomena, however, it is to be expected that they may at times coincide. The appalling pandemic of 1918 in the last months of the exhausting conflict of World War I, with massive mobilization of armies and upheaval of civilian populations, has irrevocably linked those two catastrophes. It demonstrated that virulent influenza may be more devastating of human life than war itself. Jordan2 has estimated that, in a few months, 20 million people perished; 548,000 in the United States alone; the number attacked was 50 times as great. Among the military personnel of the United States there was "an estimated total of 24,853 deaths from influenza as recorded, 469 from bronchitis, 10,341 from brochopneumonia, and 11,329 from lobar pneumonia, a grand total of 46,992. This is nearly as large a total as that of the battle deaths, American Expeditionary Forces--- 50,385." These deaths occurred among approximately "797,993 cases of influenza, 272,735 of bronchitis, 37,334 of bronchopneumonia, and 51,115 of lobar pneumonia, a total of 1,159,177 cases of respiratory diseases." 3 About 1 out of every 5 men contracted influenza in the service.
Many students of the disease have sought to explain the factors responsible for the enormity of that devastation. The clinical, pathologic, epidemiologic, and bacteriologic data have been voluminously recorded.4 It has in many quarters been accepted as the prototype of pandemic influenza, an unwarrantable conclusion since this most exceptional episode in the history of the disease
1 The author is greatly indebted to Col. John D. Morley, MC, USA (Ret.), Resident Lecturer, Department of Epidemiology, School of Public Health, University of Michigan, who gave extensive assistance in reviewing material and in the preparation of the graphs and tables dealing with incidence.
2 Jordan, E. O.: Epidemic Influenza: A Survey. Chicago: American Medical Association, 1927.
3 The Medical Department of the United States Army in the World War. Washington: U. S. Government Printing office, 1928, vol. IX, pp. 67-68.
4 (1) Thomson, D., and Thomson, R.: Influenza, With Special Reference to the Part Played by Pfeiffer's Bacillus, Streptococci, Pneumococci, etc., and the Virus Theory. Monograph 16, pt. II. Ann. Pickett-Thomson Research Lab. 9: 1-640, November 1933. (2) Thomson, D., and Thomson, R.: Influenza, With Special Reference to the Complications and Sequelae, Bacteriology of Influenzal Pneumonia, Pathology, Epidemiological Data, Prevention and Treatment. Monograph 16, pt. II. Ann. Pickett-Thomson Research Lab. 10: 641-1477, May 1934.
cannot be considered typical. Among other criteria suggested as being characteristic of pandemic influenza in contrast to that of interpandemic years are (1) a cycle of approximately 30 years; (2) the tendency for there to be three waves, the first a mild widespread disease, the second a severe autumnal epidemic with high fatality, the third of lower incidence but high fatality and less constant in occurrence; (3) a greater independence of season; (4) greater and more rapid dispersion; (5) a greater influence upon general mortality; and (6) a different age distribution so that the incidence in old people is less than that in the younger, especially middle age, groups. In many respects, these epidemiological generalizations have few supporting data other than those of 1918, and most of the other criteria appear to measure severity of the disease. Confronted with this vast occurrence and the lack of adequate information as to the nature of the causative agent, interpretations of the conditions responsible for the 1918 pandemic have inevitably considered the dislocations and crowding of populations by wartime conditions to be essential elements in the development irrespective of the biologic characteristics of the microbial agent involved.
In the latter case, the various bacterial pathogens of the respiratory tract were extensively studied and Hemophilus influenzae, while considered an important contributor to severe disease, was not believed to meet the requirements of the specific inciting agent of the, epidemic. Realization of the role of beta hemolytic streptococci and of staphylococci in severe pulmonary disease. was heightened. But beyond these was a progressive development of the idea that a highly virulent virus was involved, and a number of studies were made in efforts to demonstrate its presence. No conclusive or consistent results were obtained, even from the intensive efforts of Rosenau and others,5 to transmit the disease to human volunteers. It is interesting and surprising that apparently no material from patients was kept which could be subjected to later study for virus. Nevertheless, it seems probable that the autumnal epidemic of 1918 was initiated by a virus of high virulence in association with a high prevalence of potent bacterial pathogens. It is unlikely that this inciting agent was one with which the general population was completely inexperienced because all evidence emphasizes that the greatest proportion of the population did not take sick, indicating a resistance acquired earlier. Moreover, the fundamental characteristics of the disease clearly suggest that it was of similar behavior to influenza known before and since that time. As later data will make clear, the etiologic identity of the "waves" cannot be unreservedly assumed. Thomson and Thomson indicated that units affected in the spring prevalence were relatively resistant in the fall, although "seasoning" as such did not prevent infection since veterans and recruits were attacked in the autumn in organizations which had escaped the spring experience.
5 Rosenau, M. J., Keegan, w. J., Goldberger, J., and Lake, G. C.: Experiments Upon Volunteers to Determine the Cause and Mode of Spread of Influenza, Boston, November and December 1918. U. S. Pub. Health Serv. Hyg. Lab. Bull. 123: 5- 41, February 1921.
The relative helplessness with which prevention or treatment could be approached is apparent. Apart from the possible use of antipneumococcal serum in a limited fashion for treatment of specific cases, treatment was essentially palliative. A few studies were concerned with the use of convalescent serum. In the main, however, prompt bed rest, quiet, and simplified diet were relied upon. The handling of empyemas was revolutionized. In some instances, an intelligent effort was made to limit the opportunity for transmission of pathogens by segregating, for example, those with streptococcal infections from others. Along with these went efforts to prevent or reduce crowding by increasing space per man in barracks and in transportation and by avoiding congregations. The hygiene of housing and of person, together with isolation and quarantine, were the armamentarium of prevention.
Experience during World War I
During the period of World War I and the pandemic of influenza, one of the important agencies utilized in the campaign against respiratory diseases was the Pneumonia Board, appointed in 1918, at the request of The Surgeon General, by War Department Special Order No. 118, 20 May 1918. Composed of civilian and military experts in the field of respiratory and other infectious diseases, this board rendered advisory services and organized and directed investigations at posts, camps, and hospitals. The Pneumonia Board was a forerunner of the Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army which was established in 1941 through the initiative of the Preventive Medicine Service, Office of the Surgeon General.6 The latter became known as the Army Epidemiological Board (p.94).
Influenza is not especially a disease of wartime. However, conditions of mobilization, mass transportation, and crowding furnished a medium for the rapid spread and accentuation in severity of the disease. Because the microbial agents may be prevalent on a post or may become widely disseminated by transfer of personnel, influenza is a disease of great hazard to military effectiveness. Under these conditions, it appears that the military forces may suffer disproportionately iii comparison with civilian populations.
With this perspective, the onset of another war inevitably recalled the specter of 1918 and the possibility that the development of similar or greater concentrations of population would again result in epidemiologic conditions which would heighten the severity of influenza to a catastrophic level. Influenza after 1918 had reverted to its normal behavior of recurrent epidemics at intervals of a few years, varying in distribution and severity but commonly mild. This increased the tendency to conclude that interpandemic influenza was a different disease and that influenza was in fact a clinical syndrome rather than a disease entity.
6Bayne-Jones, S.: Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army. Army M. Bull. 64: 1-22, October 1942.
Experience in 1919-39
Between 1919 and 1939, 12 epidemics of influenza were recorded 7 by the United States Public Health Service on the basis of excessive mortality accompanying sharp epidemic waves of acute respiratory disease. The most prominent were those of 1919-20, 1922-23, 1925-26, 1928-29, 1932-33, and 1936-37, but others such as 1935-36 were widespread. That they were not inconsiderable is indicated by the fact that the estimated excess mortality from influenza and pneumonia in the 1919-20 epidemic was 100,000 and, in 1928-29, 50,000. Most of the remainder exhibited sharp peaks but were less widely distributed. A definite decline in pneumonia mortality began about 1929 and continued except for a rise in the epidemic period of 1935-37. Consequently, the scope of epidemics based upon excess mortality is less clearly demonstrated after 1930. A second interpretation for this alteration could be offered; namely, that the agent or agents of 1918 continued in prevalence through the 1928-29 epidemic and were replaced by milder strains thereafter. Nevertheless, the 1937 period had a sharp increase in mortality.
The experience of the Army during the interval between the two World Wars was not significantly different from that of the civilian population, and the mortality rates were extremely low. The small strength, furthermore, would give little meaning to an organizational rate except as it reflected general experience. In the annual reports of The Surgeon General, United States Army, for 1929 and 1930, it was pointed out that since 1920 there had been only the mild epidemic of influenza in 1926 until 1928 when "there occurred a more serious and generally distributed epidemic * * *. A comparatively large percentage of the strength of the Army was affected * * *. "In December of 1928, a rate was reached of 523 per 1,000 white enlisted men in the United States; in January 1929, the rate was 336. The annual admission rates are less informative, since they bisect the epidemic, but that of 81.7 per 1,000 for 1928 is the highest of the decade 1920-29. The rates for pneumonia and common respiratory disease during these years were also among the highest for the decade. The death rate from pneumonia and influenza was, however, not proportionately elevated.
Special attention is called to a year such as 1936 when, in certain regions among the civilian population, influenza reached the level of sharp epidemics during the early months; then in December the peak of the 1936-37 pandemic spread was rapidly approached. The first was influenza B, the second influenza A.8 The latter was worldwide and typically influenzal. Moreover, it was
7 (1) Collins, S. D.: Influenza-Pneumonia Mortality in a Group of About 95 Cities in the United States, 1920-29.Pub.Health Rep. 45:361-406, 21 Feb. 1930. (2) Collins, S. D., and Gover, M.: Influenza and Pneumonia Mortality in a Group of About 95 Cities in the United States During Four Minor Epidemics, 1930-35, With a Summary for 1920-35.Pub. Health Rep. 50:1.668-1689, 29 Nov. 1935. (3) Gover, M.: Influenza and Pneumonia Mortality in a Group of 90 Cities in the United States, August 1935-March 1943. With a Summary for August 1920-March 1943. Pub. Health Rep. 58. 1033-1061, 9 July 1943. (4) Collins, S. D.: Age and Sex Incidence of Influenza in the Epidemic of 1943-44, With Comparative Data for Preceding Outbreaks.Pub. Health Rep. 59: 1483-1503, 17 Nov. 1944. (5) Collins, S. D.: Influenza and Pneumonia Excess Mortality at Specific Ages in the Epidemic 1943-44, With Comparative Data for Preceding Epidemics. Pub. Health Rep. 60: 821-835, 20 July; 853-863, 27 July 1945.
8 Francis, T., Jr.: Epidemiological Studies in Influenza. Am. J. Pub. Health 27: 211-225, March 1937.
identified etiologically in many parts of the world. Among white enlisted men in the Army in the United States, the admission rate for 1937 rose to 50.1 per 1,000 average strength, but seasonal data are not available. There is evidence, nevertheless, that the 1936-37 epidemic was sharply expressed in the Army, although no significant increase in mortality occurred. In 1938-39, a mild prevalence of a spotty nature was present (charts 12 and 13).
Influenza, then, in the 20 years since 1919 had returned to its former status of recurrent epidemics at short intervals, often so mild as to be unnoticed but with certain episodes of pandemic distribution and of sufficient severity to cause considerable alarm and disturbance in the general population. That it was a disease of potential severity was clearly apparent since even the mild prevalences tended to cause a heightened mortality from respiratory disease. The excess mortality remained a valuable index of the spread and severity of epidemics and even of their recognition. Reports based upon clinical diagnosis were, as always, unreliable since many factors, including publicity or special instructions, had a large influence in this respect. Army data show this effect clearly, as will be illustrated later, in the lack of reports of influenza from some areas when an epidemic was known to be occurring, or high reports of influenza in prevalences of acute respiratory disease known not to be identifiable as influenza. However, in most instances, the character of the epidemic curve and the distribution among troops of abrupt rapid epidemics of nonbacterial acute respiratory disease readily suggest its nature. The occurrence of the disease and the factors which govern it remained essentially unaffected at the onset of World War II .
Epidemic Influenza, 1940-45
Experience in 1940
The Army began its expansion program in 1940, and the draft was adopted. The increase in strength began slowly in June, then rapidly in October, November, and December. This and the industrial program brought together a large number of individuals from diversified areas under conditions furnishing ready opportunity for the rapid spread of respiratory infections. However, in general, the health of the Army and the United States during this period was excellent.
Early in 1940, a limited epidemic of mild influenza occurred, first in the Southeastern States and shortly afterward in New York. This was the out break from which influenza virus, type B, was first isolated.9 In the civilian population, it was said to be limited to the eastern part of the United States, but serologic data demonstrated it to be more widely dispersed.10 The admission rates for influenza in the Army show a moderate rise in the Third, Fourth, and Fifth Corps Areas during the months of January and February. In general, the United States Army within the continental limits had a low incidence of influenza for the first half of the year as compared with the previous
9 Francis, T., Jr.: A New Type of Virus
From Epidemic Influenza .Science 92: 405-408, 1 Nov. 1940.
5-year average. The admission rate for common respiratory diseases for the same period, however, was in general higher than the 5-year average. Influenza B was recognized in southern England,11 and, in the summer of 1940, it was prevalent in Cuba.12 The recognition of this disease and means for identification were extremely important for proper understanding of the problem.
In June and July 1940, well-marked epidemics of influenza A occurred in Cuba and Puerto Rico. There was a sharp rise in the admission rate to 126.4 for influenza among the Puerto Rican troops in June followed by a moderate rise to 93.9 in July among the continental troops stationed on the island, but in August no cases were reported.
At this same time, an epidemic of mild influenza was reported from Argentina.13 This outbreak reached its peak in the Argentine Navy in the week ending 21 July 1940, in the Army during the following week, and in the civilian population in the week ending 4 August.
In August, the admission rates for influenza showed a sudden rise in the Philippine Islands. The incidence during the month was twice as high among Filipino troops as that reported for United States troops stationed there. Unfortunately, the data for admissions in the overseas departments are not available for the remaining months of 1940 (September to December).
During 1940 in Australia, especially in military camps, extensive epidemics of pharyngitis and tracheitis occurred. Influenza was not isolated until September when more typical cases occurred in a military camp and in a small hospital outbreak.14
Influenza was noted in Hawaii in the middle of September 1940 and declared epidemic on 26 September. Reporting was then made mandatory until 31 December. Approximately 16,500 cases were reported. The majority of these were from the island of Oahu, including Honolulu. The epidemic peaked sharply during the middle of October. Doolittle 15 stated the impression that the disease came from the West and suggested that it was introduced by a Japanese training ship from the Japanese Mandated Islands where an epidemic was prevalent. The influenza incidence among white enlisted troops stationed in Hawaii during 1940 was 65.3 per 1,000 average strength per year. The highest incidence for white enlisted melt for the year was reported in the United States (77.6) with Hawaii in second place.
In November 1940, the admission rates for influenza in the Ninth Corps Area showed a sharp rise which reached its peak in the 4-week period of
11 Andrewes, C. H., Glover, R. E-, Lush, D., Hudson, N. P., and Stuart-Harris, C. H.: Influenza in England in 1940-41.Lancet 2: 387-389, 4 Oct. 1941.
12 Lennette, E. H., Rickard, E. R., Hirst, G. K., and Horsfall, F. L.: The Diverse Etiology of Epidemic Influenza. Pub. Health Rep. 56: 1777-1788, 5 Sept. 1941.
13 Sordelli, A., Taylor, R. M., and Parodi, A. S.: Estudio de los virus de la epidemia de influenzao currida on la Argeninga durante el año 1940. Rev. d. Inst. bact, Buenos Aires 10: 265-274, December 1941.
14 (1) Rudd, G. V.: Influenza Epidemic at Puckapunyal. M. J. Australia 1: 7-9, 4 Jan. 1941. (2) Burnet, F. M., and Foley, M.: Two Methods for the Detection of Influenza Virus in Human Throat Washings Without the Use of Ferrets. M. J. Australia 1: 68-72, 18 Jan. 1941.
15 Doolittle, S. E.: Clinical Observations During the 1940 Epidemic of Influenza in Honolulu. Proc. Staff Meet. Clin., Honolulu 7: 1-8, March 1941.
December. During this same period, the Fifth Corps Area had a very high incidence (1,444 per 1,000 per annum based on the 4-week period). The Eighth Corps Area also recorded its highest rates during December. The other six corps areas reached their highest incidence during the 5-week period of January 1941. The First, Second, and Sixth Corps Areas lead a relatively low number of cases of diagnosed influenza (below 200 cases per 1,000 per annum in the highest period), although definite epidemic peaks were attained. The rate of admissions in white enlisted men in the United States was 77.6 for 1940, which was approximately four times that for 1939, 20.3. Admissions for common respiratory disease in each corps area, except the Fifth Corps Area, showed a sharp rise coincident with the rise in influenza. The incidence of these diseases remained generally high until March in contrast with the much more rapid subsidence of influenza. The combined annual rate for common respiratory diseases and influenza was nearly 1,200 for the entire Army in the United States for 1940-41 (chart 14).
A widespread epidemic of influenza occurred in the civilian population at the same time.16 The notable feature of this outbreak was the rapidity of spread from the Pacific Coast eastward throughout the United States and Canada. The peak of incidence in the Pacific Coast States was reached in mid-December. The West South Central and Mountain States reached their peak in late December or the first week in January, the East South Central and South Atlantic States the second week in January, and the East North Central and Middle Atlantic States during the third week of January. However, the New England States reached their peak during the second week in January. The spread of the disease as shown in the Metropolitan Life Insurance Company survey 17 seemed to follow three main paths: (1) The southernmost route across the Southern and Gulf States spread most rapidly and showed the most ordered progress; (2) the path across the middle of the country was not quite as rapid; (3) the northernmost route showed the slowest rate. The peak of the incidence in South Dakota was in early February and in Iowa and Wisconsin in mid-February. As the admission rates for the Army are given for 4- or 5-week periods, no such orderly progress of the disease was discernible.
Clinically the disease was a mild acute febrile illness with abrupt onset associated with mild myalgia, some lassitude, but little prostration. Complications were rare. Of 19,609 cases occurring among Army personnel in the United States, 57 developed pneumonia. Only 1 death from influenza was reported in the Army for 1940 and only 3 deaths from acute primary pneumonia.______
16(1) See footnote 7 (4) and (5), p. 88. (2) Brown, J. W., Eaton, M. D., Meiklejohn, 0..; Lagen, J. B., and Kerr, W. J.: An Epidemic of Influenza. Results of Prophylactic Inoculation of a Complex Influenza A-Distemper Vaccine. J. Clin. Investigation 20: 663-669, November 1941. (3) Sulkin, S. E., Bredeck, J. F., and Douglass, D. D.: Epidemic Influenza: Epidemiological, Clinical, and Laboratory Aspects of the 1940-41 Outbreak in St. Louis. Am. J. Pub. Health 32: 374-380, April 1942.(4) Pearson, H. E., Eppinger, E. C., Dingle, J. H., and Enders. J. F.: A Study of Influenza in Boston During the Winter of 1940-41. New England J. Med. 225: 763-770, 13 Nov. 1941.
17 The Course of the Recent Influenza Epidemic Statist. Bull. Metrop. Life Insur. Co. 22 (No. 4): 3-6, April 1941.
The excess mortality recorded in the civilian population was slight, but, according to the recorded rates of the Army in the continental United States, this was the highest epidemic of the war period.
It was during this explosive outbreak of influenza that the planning and guidance exercised by the reorganized Preventive Medicine Service, Office of the Surgeon General, under the immediate direction of Lt. Col. (later Brig. Gen.) James S. Simmons, MC, resulted in the development of a new and powerful means for combating infectious diseases in the Army. Since the start of World War II in Europe in 1939, followed by the expansion of the Army, the Preventive Medicine Service had seen the necessity for preparing in advance for dealing with new and large problems. It was foreseen that there would be urgent need for the services of the best civilian specialists in the field of infectious diseases. The Pneumonia Board of 1918, previously mentioned, was recalled as an example of the kind of organization that would be needed. Proceeding along these lines, Colonel Simmons drew up a plan for a greatly enlarged and strengthened civilian body of this type and, on 27 December 1940, recommended to The Surgeon General that the plan be forwarded to The Adjutant General for approval. This was done the same day by Maj. Gen. James C. Magee, The Surgeon General, and, on 11 January 1941 by order of the Secretary of War, the Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army was established. Within a a few months, a number of civilian commissions on various infectious diseases were formed, and the Commission on Influenza was one of the first to be established. The Board and its commissions were attached to, and administered by, the Preventive Medicine Service, Office of the Surgeon General.
Experience in 1941-42
During the remainder of the year 1941, the admissions for influenza and the common respiratory diseases followed the usual seasonal pattern and fell to the lowest level in July. However, the incidence of acute respiratory disease during the summer season remained higher than the average for the preceding decade.
With the onset of open hostilities in December 1941, the mobilization for war was tremendously increased. The very rapid induction of men when housing facilities were inadequate caused definite overcrowding. It was necessary to reduce the floor space per man in barracks from 50 to 40 square feet, and a considerable proportion of troops were housed in tents. Such Housing conditions undoubtedly contributed to the moderately high admission rates for acute respiratory disease in the winter of 1941-42, but no epidemic of influenza was encountered.
Experience in 1942-43
In the summer of 1942, the military forces were still increasing rapidly. New groups of recruits were constantly entering camp, troop movements were
continuous, and the expansion frequently resulted in overcrowding on trains and in barracks, especially in induction and training centers. There was at the same time a migration of civilians into overcrowded industrial centers. In keeping with the recurrence of influenza A every other year since 1932, 1942-43 was scheduled for an epidemic with conditions in the population apparently favorable to the disease. Studies of vaccination were linked to this premise, and close observation was maintained. Influenza A was epidemic in Australia in May 1942, 18 but elsewhere the disease did not appear in significant amount, and in the United States it was not found.
On the other hand, noninfluenzal acute respiratory diseases and atypical pneumonia rose to epidemic heights and maintained a high level throughout the season when respiratory diseases were expected to occur. In the continental United States, a peak of 530 per 1,000 per annum for January 1943 slowly receded over several months. The disease was particularly prominent in recruits and in other epidemiologic characteristics differed from the usual epidemics or influenza.
Experience in 1943-44
Although influenza was inconspicuous during the preceding winter, each succeeding season carried the possibility of a severe epidemic which, with crucial operations mounting in many parts of the world, might be critical. Advance information was desirable. The virus laboratories of the Commission oil Influenza of the Army Epidemiological Board were still alert in various areas, and the continued high incidence of respiratory disease held the attention of all medical agencies. Commission investigators identified influenza B widely but largely subclinically in two institutions in Michigan during March and April; two cases of type A were also found. Sporadic cases of type B were also detected at Fort Custer, Mich., and among students at the University of Michigan.19 A small amount of influenza B was identified in Australia .20
In May, three sporadic cases of influenza A were identified at Fort Custer, and virus was isolated.21 Serologic examination demonstrated that a limited outbreak in April among interns in a New York hospital was influenza A and Eaton detected five cases of influenza A among students at the University of California in April and isolated a strain of virus. Here were striking evidences of a scattered low-grade circulation of influenza without epidemic conditions. Epidemic influenza in July was reported in Hawaii but not iden-
18 Burnet, F. M., Beveridge, W.I.B., Bull, D. R., and Clark, E.; Investigations of an Influenza Epidemic in Military Camps in Victoria, May 1942. M. J. Australia 2: 371-376, 24 Oct. 1942.
19 Salk, J. E., Pearson, H. E., Brown, P. N., Smyth, C. J., and Francis, T., Jr.: Immunization Against Influenza With Observations During an Epidemic of Influenza A One Year After Vaccination. Am. J. Hyg. 42: ;107-322, November 1945.
20 Beveridge, W.I.B., and Williams, S. E.: Sporadic Occurrence of Influenza in Victoria During 1943. M. J. Australia 2: 77-80, 22 July 1944.
21 Francis, T., Jr.: The Development of the 1943 Vaccination Study of the Commission on Influenza. Am. J. Hyg. 42: 1-11, July 1945,
tified by type. Scattered flurries in military camps were observed in Canada.22 In the late spring and summer, limited scattered bursts of influenza A were identified in British civilians; 23 in August a localized unidentified epidemic occurred among United States troops in Southern Base Section. Much of the foreign information was only known through subsequent publication or through informal channels.
The possibility was recognized that these episodes might be the forerunner, or first wave, of a serious autumnal experience. With plans for evaluation of vaccine by the Commission on Influenza actively proceeding, the new strain of virus was incorporated in the vaccine; the continuous lookout for influenza was enlarged to include a greater number of listening posts maintained by Commission members throughout the nine service commands; and a formal arrangement for reporting was concluded. Samplings of throat washings and blood were obtained at intervals from patients with upper respiratory disease even though the diseases did not resemble influenza clinically. The results from each observation post were communicated to each of the others and to the Preventive Medicine Service, Office of the Surgeon General, at biweekly intervals.
On 17 and 18 November 1943, several patients presenting a picture which resembled influenza were observed in the ASTP (Army Specialized Training Program) unit at the University of Michigan. Throat washings given to ferrets elicited a typical reaction, and transfer of ferret material to eggs permitted identification of influenza virus, type A. On 22 November, Dr. E. R. Rickard in St. Louis, Mo., reported that between 11 and 18 November what appeared to be an epidemic of influenza had occurred in the ASTP unit at St. Louis University, involving 100 out of 550 men. He also reported that in one of the groups under observation at the University of Minnesota at Minneapolis, a sudden outburst of 20 cases had occurred on 21 November. Type A influenza virus was identified by direct inoculation of throat washings into the allantoic sac of eggs. All other investigating groups were notified that influenza A had been identified in both the Sixth and Seventh Service Commands.
Word was received
from Lt. Col. F. B. Lusk, MC, Chief, Medical Service, Station Hospital,
Custer, on 15 November 1943, that a sharp increase of febrile
respiratory disease had taken
place. Material obtained from patients becoming ill there during the
next week demonstrated
that almost all of these patients had influenza A. After this time the
spread of the disease was
rapid, and subsequent reports from Commission members indicated that,
within 7 to 10 days,
cases had begun to appear over a great part of the United States.
From July 1943 to the week ending 6 November 1943, the weekly rates for influenza and common cold for the entire Army in the continental United______
22 Hare, R., Hamilton, J., and Feasby, W. R.: Influenza and Similar Respiratory Infections in a Military Camp over a Period of Three Years. Canad. J. Pub. Health 34: 453-464, October 1943.
23Andrewes, C. H., and Glover, R. E.: The Influenza "A" Outbreak of October-December 1943. Lancet 2: 104-105, 22 July 1944.
States had remained at a level of approximately 100 per 1,000 per annum and up to 30 October in none of the service commands had rates reached 150.
In the week ending 6 November 1943, the first rises to levels greater than 150 were noted in the Sixth and Seventh Service Commands, to greater than 200 in the weeks ending 13 and 20 November, respectively; the two areas proceeded rapidly to reach their respective peaks of 1,279 and 1,050 the week ending 4 December (table 19). The first sharp increase recorded at posts in these commands was at Fort Custer where rates rose from 113 in the week ending 30 October to 441, 1,075, and 1,212 in the weeks of 6, 13, and 20 November, respectively. It was here, too, that influenza A was identified in May 1943. The First, Second, Third, and Fifth Service Commands reached heights of greater than 200 during the week ending 27 November and attained their peaks the week of 11 December. Rates in the Fourth, Eighth, and Ninth Service Commands, although giving evidence of increased prevalence of influenza, did not exceed 200 until the week of 4 December. The peaks in these three commands were considerably lower and later in their occurrence than elsewhere.
It is of interest to note that on 24 November, at which time the recorded figures give little indication of influenza in the Eighth Service Command, patients with influenza A were identified in the station hospital at Fort Custer. These men had entrained 48 hours earlier in Texas (located in the Eighth
Service Command) and lead remained in the troop train but became ill before arrival at Fort Custer.
The highest rates for the entire Army in the continental United States were 631 and 593 in the weeks of 11 and 18 December. By 7 January 1944, the epidemic period had practically ended in all areas, and the rate for the entire Army fell below that for the previous year but, due to the seasonal increase in upper respiratory infection of other etiology, in no command did the rate return to the level which had existed in early November. That the continued incidence was not due to influenza A is seen in the reports of the different investigators who, with the exception of those in California, considered the epidemic prevalence of cases to have ended before 1 January. Further support for this conclusion is found in the results of studies made in the respiratory wards at Fort Custer on 28 January 1944 when serologic tests in recent febrile respiratory admissions were all negative for influenza A although similar studies on 20 November and 27 December were almost uniformly positive. Precise information of the epidemic is largely derived from the Commission studies.24
In an analysis of the reported cases of influenza during the 1943-44 epidemic among the civilian population, Holland and Collies 25 found that the maximal incidence of the disease for the country as a whole occurred between 25 December 1943 and 4 January 1944, 2 to 3 weeks later than that noted in the Army. They conclude that the 1943-44 epidemic was larger than any since the period 1918-20" For a group of 90 large cities, the excess mortality during the 11 weeks from 21 November 1943 to 5 February 1944 was 50 per 100,00 population in comparison with 65 per 100,00 for the epideic of 1928-29 and 598 for the pandemic of 1918-19. Comparable data are not available for the 1936-37 epidemic, but a statement has been made that it wa smaller than earlier outbreaks.
Collins 26 compared the results of house-to-house canvasses in Baltimore during the 1943-44 epidemic with those in other communities during 12 other epidemics since the beginning of 1918. He states, "considering actcual rates, the recorded incidence for all ages in the 1943-44 outbreak was higher than in any other epidemic since that of 1918-19; the incidence among children under 10 years of age approximated that in 1918-19, and the incidence above 40
24 (1) Rickard, E. R., Thigpen, M., and Crowley, J.H.: Vaccination Against Influenza at the University of Minnesota- Am. J. Hyg. 42: 12-20, July 1945. (2) Hale, W. M., and McKee, A. P.: The Value of Influenza Vaccination When Done at the Beginning of an Epidemic. Am. J. Hyg. 42: 21-27, July 1945. (3) Eaton, M. D. , and Meiklejohn, G.: Vaccination Against Influenza: A Study in California During the Epidemic of 1943-44. Am. J. Hyg. 42: 28-44, July 1945. (4) Hirst, G. K., Plummer, N., and Friedewald, W. F.: Human
Immunity Following Vaccination With Formalinized Influenza Virus. Am. J. Hyg. 42: 45-56, July 1945. (5) Salk, J. E. Menke, W. J., Jr., and Francis T., Jr.: A Clinical Epidemiological and Immunological Evaluation of Vaccination Against Epidemi Influenza. Am. J. Hyg. 42: 57-93, July 1945. (6) Magill, T. P. Plummer, N., Smillie, W. G., and Sugg, J. Y.: An Evaluation of Vaccination Against Influenza. Am. J. Hyg. 42: 94-105, July 1945.
D. F., and Collins, S. D., The
Influenza Epidemic of the Winter of 1943-44 in the
United States: A Preliminary Summary. Pub. Health Rep.
59. 1131-111, 1 Sept. 1944.
years was greater than in 1918-19. The percentage of the total cases that were complicatd by pneumonia in the 1943-44 epidemic was far below the figure for any other epidemic for which data are available." Nevertheless, the pneumonia rates among persons over 25 years of age correspond closely to those recorded in this age group during the epidemic of 1928-29.
The data from all sources indicate, then, an epidemic of high incidence making its earliest prominent appearance in the North Central States in the first half of November 1943, spreading rapidly to a peak in December, and then promptly declining to the seasonal level of respiratory disease, thereby occupying a total of approximately 6 weeks for the evident epidemic period. It is of interest that, in the Gulf, Southwestern and Pacific States, the onset was slower and the peak lower and later than in other parts of the country. The data indicated that in terms of incidence the outbreak was of major proportions but the complications and case fatality rates were low, although its effect on total mortality by virtue of the high incidence was greater than the case fatality rate would indicate.
In the entire Army, only 8 deaths occurred among influenza patients and 290 deaths among admissions for pneumonia oter than primary atypical. Even a rough estimate of case fatality rates is unreliable since reported and summarized data are inconsitent. Of the total 89,764 cases recorded for the total Army in 1943, 69,840 were in the United States with 5 deaths and a case fatality rate of 0.01 percent. In the European theater, 4,717 cases are recorded with 1 death (table 20).
European Theater of Operations.-American troops in the European theater experienced an epidemic of influenza A in the fall of 1943, which reached its peak about 2 weeks earlier than in the United States. 27 After a suggestive rise in reported cases of acute respiratory disease in the last week of October and the first week of November, there was an extremely rapid incrase to maximum annual admission rates of 1,079 per 1,000 strength for the week 26 November 1943. The decline of the epidemic was as sharply marked as its rise. By the end of December, the rate was 387. Virus A was demonstrated to be present in each of the principal base sections by serologic studies. Influenza B was not found. The disease was described as mild and uncomplicated with an acute onset and lasting only a few days. Constitutional rather than local symptoms predominated. The outbreak was almost completely unassociated with an increase prevalence of primary and secondary penumonia. There were no death.
According to Gordon, admission rates for common respiratory diseases, including influenza, among Negro troops were much less than for white troops in the theater. The maximum rate for the two groups occurred during the week of 26 November 1943. The rate for white troops was 1, 129 and for Negro troops, 477.
27 Gordon, John E.: A History of Preventive Medicine in the European Theater of Operations, U.S. Army, 1941-45, vol. I. (Official record.)
The civilian population of the United Kingdom had a similary epidemic at approximately the same time.28 It differed from that of the United States Army principally in respect to mortality. The maximum number of 1,148 deaths from influenza was reported during the week of 11 December 1943. This was 2 weeks later than the peak for the military cases. The deaths were largely among the older age group.
Other overseas theaters. -Alaska reported an explosive epidemic suggestive of influenza among military and civilian populations in the first 2 weeks of April 1943, and, again beginning on 21 December 1943, there was a sudden increase in the incidence of acute respiratory disease at Fort Greely, Alaska, which quickly reached a peak and subsided within 1 month. Small outposts were not involved. A total of 535 cases were admitted to hospital and 1,043 to quarters. Average duration of hospital and quarters stay was 5 and 4 days, respectively. The clinical description was "typcal" of influenza. There was no recurrence and no deaths.
Dr. J. H. Dingle, a member of the Commission on Acute Respiratory Diseases, investigated a mild epidemic of influenza that occurred in Puerto
28 See footnote 23, p. 96.
Rico in July 1943. It was estimated that 500 cases occurred among the civilian population of San Juan. There was no pulmonary involvement. Troops in Saint Thomas had a small outbreak of approximately 50 cases.
During July and August, an epidemic of acute respiratory disease, probably influenza, occurred in the 65th Infantry Division (Puerto Rican Regiment) with 441 admissions. There were 452 cases among employees of the Panama Engineer Division. Cases were also reported in Camps Sabanita and Coiner, Canal Zone.
Hawaii reported an epidemic of mild influenza in late June and July.
In the Southwest Pacific and China-Burma-India theater no influenza outbreak were reported.
In the North African theater, especially in Italy, no evidence of influenza in significant amount was discerned.
Variations in behavior. -The commission on Influenza reported that differences in the behavior of the epidemic in adjacent units were clearly observed. For example, at the University of Minnesota, the incidence among the total study population was 5.9 percent, while in another group it was 38 percent. At the University of Michigan, a wide variation in involvement of different companies of the ASTP unit was observed, two companies having but a single hospitalized case each, while from another company not in the study 20 percent were hospitalized. The commission on Acute Respiratory Diseases had recorded a number of significant features. At Camp Mackall, N.C., the troops were all seasoned men with 6 months or more of training. The epidemic appeared in all parts of the camp in an explosive fashion with 64 percent of the admissions occurring in a period of 5 days. Approximately half the admissions in the 11th Airborne Division occurred among the artillerymen with a rate of 8.8 percent, which comprised less than one-fifth the total strength. Very low admission rates, approximately 1.0 percent, were observed among 2 of the 3 infantry regiments. It was thought that "the explosiveness and short duration of the epidemic at Camp Mackall appear to be related to the environment and activities of the troops. There was marked crowding in the barracks; the inhabited area of the post was small; and all groops shared common transportation facilities." At this camp, 29 cases of pneumococcal pneumonia, most of which were type I, occurred during the epidemic period with a rather prompt disappearance thereafter.
At Pope Field, Fort Bragg, N.C., a detachment of glider mechanics had sick men with them on arrival at the post. They were put into quarantine under crowded conditions and in 7 days had a total admission rate of 35 percent. The remainder of the units in adjacent barracks had no contact with the affected unit. Cases occurred over a month's time with a total admission rate of 5 percent. A contrasting episode was that of the 326th Glider infantry Regiment which arrived by train from the Midwest; a large number of admissions occurred in the first 2 days, but then the incidence dropped and remained low as they were moved into uncrowded barracks and field activities. No explosive outbreaks were seen at Fort Bragg in troops engaged in continuous
field training. These reports emphasized, too, that at Fort Bragg the virus was repeatedly introduced by men who had acquired their infection in widely separated areas of the country. This was also noted at Fort Custer where troops arriving promptly from Texas were sick although the disease had not been recognized there.
General Depot G-18 of the Western Base Section had a strength of 5,737 men divided into eight camps. The first five were situated near Sudbury, England, and Nos. 6, 7, and 8 were at Eggerton, several miles away. On 3 November, the first probable patient with influenza from C Company, 131st Quartermaster Regiment (TRK), Camp No. 2, reported to the dispensary with headache, backache, prostration, and an elevated temperature. Within 12 hours, the medical officer developed the same symptoms. The following day 21 men of C Company were ill. On 5 November cases began to develop in the 445th Engineer Base Company, on 7 November in 608th Engineer Light Equipment Company and on 8 November in the 887th Ordinance Ammunition Company. Altogether, Camp No. 2 with 837 men had 121 patients in hospital with influenza, practically all of whom developed the infection between the 4th and 11 of November and belonged to one or other of the four companies noted.
Camp No. 1 was located in the same vicinity as Comp No. 2, and shared the same dispensary. The outbreak in this camp extended over the same period. Of 849 men, 72 were admitted to hospital with influenza.
Camp No. 3, housing the 534th Quartermaster Service Battalion, a colored labor unit, had no known association with any other camp except for an exchange of labor with the 2d platoon of D Company located at Camp No. 8. The outbreak of influenza began at Camp No. 3 on 14 November with the hospitalization of six men. The following day so many new cases appeared that two empty barracks were converted into a camp infirmary. During the period 14 to 24 November, this unit had 111 cases of respiratory disease. The infection spread to 2d platoon, D Company at Camp No. 8 and 26 cases were reported between the 22d and 25th of November. With the exception of this platoon there were few cases of respiratory infection at Camp No. 8.
Camp 4, with 689 men, sent 15 to the hospital between 17 November and 25 November, and the daily sick call averaged about 15 which was only slightly higher than had held in October.
Camp 5, an Air Corps Depot having little association with other camps, had no cases of influenza.
Camps 6 and 7, located several miles from the other camps, likewise had very few cases of respiratory disease.
It is clearly demonstrated that respiratory disease spread rapidly from one group to another within an incubation period of about 24 to 48 hours. Association of groups was a much more important factor than kind of work or type of quarters.
It was recognized from the start that the epidemic disease affected recruits and seasoned men alike. In fact, at many posts this feature was
emphasized to differentiate between influenza and the acute respiratory disease which was preponderant in recruits. At Fort Bragg, it was precisely observed that the incidence of influenza A was not different among the two classes of men living under comparable conditions. This may well be indicative of the fact that infection with influenza is not a year-in, year-out process but one which takes place primarily in epidemic periods; alternatively it may also be interpreted to demonstrate that immunity is not durable or that strain variation is involved.
As previously mentioned, in the European theater the peak incidence of influenza in Negro troops was less than half that in white troops. No other data of this nature are available.
In reviewing the variations that were encountered, it becomes increasingly convincing that, apart from the need for exposure of susceptibles to disease, the most important factor in determining the behavior of epidemic influenza within limited units is that of crowding, particularly when a high rate of change in the population exists.
A few instances are recorded of the epidemic moving into units in which beta hemolytic streptococcal infection was prevalent.29 The incidence of respiratory diseases was highest thoughout the epidemic in the Seventh Service Command, where streptococcal disease was highly prevalent. There was in these areas, however, no evidence that the bacterial invasion was accentuated by influenza as was clearly the case in 1918. Coburn 30 has indicated that influenza had a definite influence upon the behavior of streptococcal infection in naval units, and, at the United States Naval Training Center at Farragut, Idaho, the occurrence of influenza was clearly related to an exaggeration in spread and severity of streptococcal disease. There are also numerous studies indicating that pneumococcal penumonia was more prevalent during the epidemic, but in other instances as at Sioux Falls, S. Dak., where pneumonia was epidemic, Hodges and MacLeod 31 conclude that influenza was not unduly prominent as a participating factor.
Special concern was attached to the transport of troops during the epidemic. Serious trouble was not encountered in overseas movements although a convoy of 63,750 troops had 7,529 (12 percent) sick calls for respiratory disease while en route to Great Britain inDecember; 962 men were hospitalized and 86 were evacuated to hospital on debarkation.32 In another instance, 23 percent of a contingent were sick aboard ship. Official recommendation was made that at all ports of embarkation a minimum of 60 square feet housing space be re-
30 Coburn, A.F.: Mass Chemoprophylasix. Th U.S. Navy's Six Months' Program for the Control of Streptococcal Infections. In United States Navy Department, Bureau of Medicine and Surgery: The Prevention of Respiratory Tract Bacterial Infections by Sulfadiazine Prophylaxis in the United States Navy. Washington: U.S. Government Printing Office, 1944, pp. 149-162.
31 Hodges, R.G., and MacLeod, C. M.: Epidemic Pneumococcal Pneumonia, IV. The Relationship of Nonbacterial Respiratory Disease to Pneumococcal Pneumonia. Am. J. Hyg. 44; 231-236, September 1946.
32 Informal memorandum, Lieutenant Cree for Colonel Gordon, 20 Dec. 1943, subject: Respiratory Disease on Transports on Shipment UT 5.
quired; this was an effort to avoid crowding and illness at the time of embarkation. 33
Control measures. - The general control measures were those designed to prevent or retard the spread of infection from person to person. Emphasis was placed on the avoidance of overcrowding by increasing the floor space per man in barracks and reducing the number of troops per car on trains. Troop movements were kept at a minimum during the outbreak. Personal hygiene and proper sterilization of messgear were stressed. During the epidemic, fatigue and exposure to cold and wetness were minimized. In high-priority units, medical inspection of troops and the hospitalization of patients with incipient disease were advocated.
The action taken by the Preventive Medicine Service of the Surgeon General's Office to maintain close touch with the epidemic situation and to gain the advantage of environmental control measure is summarized as follows: 34
1. The first definite information that epidemic influenza was occurring came on 21 November 1943. The isolation of virus A from such an outbreak was first reported on 25 November.
2. On 3 December, the Medical Statistics Division was requested to furnish the number of cases of influenza separate from common respiratory diseases.
3. All service commands, the Air Surgeon, and the Chief of Transportation were requested on 6 December to notify all stations under their jurisdiction to report by telegram all influenza outbreaks then occurring, as well as future outbreaks, to The Surgeon General. This action was taken at the request of General Simmons, and the reports were rendered under previously granted Control Approval Symbol MCE-64.
4. On 16 December, all posts over 5,000 strength were asked to telegraph weekly reports of the number of cases of common respiratory disease, including influenza and pneumonia, to service command headquarters, which was in turn, to forward a consolidated report by wire to The Surgeon General. This action followed a staff conference at which it was indicated that The Surgeon General was expected to know the current situation with respect to influenza. The reporting system thus set up reduced by a week the delay in compilation of rates, although the rates computed were, of course, estimates based on a sample only. Experience showed the estimated rates to be fairly accurate in comparison with the final returns on the monthly summary reports from all posts.
5. A report based on the telegraphic rates was made by The Surgeon General to the Secretary of War, Chief of Staff, and Commanding General,
33 (1) Coded message (routine), Chief of Transporation to all Ports of Embarkation, 19 Dec. 1943, subject: Instructions in Control Measures to Be Put Into Effect. (2) Memorandum, Chief of Staff for Commanding General, Army Service Forces, 30 Dec. 1943, subject: Considerations of Influenza Precautions With Respect to Overseas Troop Movements. (This was accompanied by a list of 15 stations designated to provide overflow capacity for regular port staging areas in an emergency.) (3) Momorandum, Commanding General, Army Service Forces, for Chief of Transportation, 6 Jan. 1944, subject: Measures to Prevent Epidemics During Troop Movements.
34 Memorandum for file, 24 Feb. 1944, subject: Summary of Developments and Action Taken During 1943 Influenza Epidemic.
ASF (Army Service Forces), on 21 December, and similar reports were rendered
at the end of the month and again on 7 January 1944.
6. On 28
December, a request was made to the Control Division, ASF, for approval of the weekly telegraphic report; it had previously been understood that such approval was unnecessary. This request was disapproved, and The Surgeon General was instructed to advise service commands immediately that the
weekly telegraphic report was no longer required. The Preventive Medicine Service, Office of the Surgeon General, informed the Commanding General, ASF, that his instructions had been carried out but indicated that this office did not concur in the objections to the report.
7. All service commands, the Air Surgeon, and the Chief of Transportation were notified by wire on 7 January
1944 that the telegraphic reports of respiratory diseases were discontinued.
8. On 15 December 1943, the Deputy Chief of Staff sent a radiogram to all major commands in the United States calling attention to control measures and authorizing hospitalization
of civilians in military hospitals when necessary. Reference was made to the maintenance of production schedules in industrial plants. Reports of influenza outbreaks in units soon to go overseas were to be telegraphed to The Surgeon General.
9. On 19 December, the Transportation Corps telegraphed all ports, giving instructions in control measures. These instructions were prepared in consultation with the Epidemiology Branch, Preventive Medicine Division, Office of the Surgeon General.
10. On 30 December 1943, the Chief of Staff sent the Commanding General, ASF, a memorandum, entitled "Consideration of Influenza Precautions With Respect to Overseas Troop Movements," accompanied by a list of 15 stations designated to provide overflow capacity for regular port staging areas in an emergency.
11. The Commanding General, ASF, in his memorandum for the Chief of Transportation, dated 6 January 1944, entitled "Measures to Prevent Epidemics During Troop Movements," forwarded a copy of the memorandum from the Chief of Staff, previously referred to.
12. The Commanding General, ASF, also sent The Surgeon General a memorandum, same subject, on 6 January, including a copy of the memorandum from the Chief of Staff and attached list of stations. The Surgeon General was directed to issue necessary technical instructions and report recommendations for the modification of present procedures. The Surgeon General's endorsement on 20 January stated that an article on influenza would be published shortly in a medical technical bulletin and recommended that directives be published requiring a minimum of 60 square feet of space per man in barracks.
13. The Chief, Preventive Medicine Service, Office of the Surgeon General, sent a draft of medical technical bulletin entitled "Influenza," to the Executive Officer on 28 January.
14. On 29 January, a directive entitled "Measures to Prevent Epidemics of Respiratory Diseases," was sent to all defense commands, service commands,
ports, and technical services. This was substantially the same as the letter recommended by The Surgeon General.
Cooperation with civilian groups.-Because of the potentialities of a severe outbreak of influenza similar to the 1918-19 epidemic, plans were made by the Preventive Medicine Service, Office of the Surgeon General, for the Army to give assistance in the medical care of civilians in cases of emergency. Medical Department personnel, supplies, hospitalization, and transportation were to be made available to the maximum extent after the first and second echelon facilities consisting of the local and State physicians and facilities, American Red Cross, United States Public Health Service, and Office of Civilian Defense, were exhausted. Hospitalization of civilian personnel was authorized, and each service command and post surgeon made plans to be put into effect if indicated. As the epidemic remained generally mild, these procedures were not used.
Experience in 1944
With the abrupt subsidence of the epidemic of influenza A in the winter of 1943-44, the admission rates for respiratory diseases within the continental limits of the United States continued to decline rapidly and remained below the average level of Army experience for the decade 1930-39 (chart 13). After January, they also readied a level well below that of the three preceding winters. The Army at this time was composed largely of seasoned troops since the rate of induction was low as compared with the 3 preceding years.
Experience in 1945
A small seasonal rise in rates occurred during the winter months 1944-45 but that for troops in the United States remained under 200 admissions per 1,000 per annum. The overseas theaters had similar low rates for acute respiratory disease. No outbreaks of influenza occurred. However, the Commission on Influenza continued a more extended alert for detection by investigating unusual rises in admissions for acute respiratory disease and sampling cases in respiratory, wards of various Army hospitals. Investigation of an outbreak of illness in the Antilles Department reported to be influenza revealed it to be infectious mononucleosis; nevertheless, an opportunity was provided for setting up a center for the identification of influenza in the area.35
Beginning in March 1945, small localized outbreaks of influenza B occurred in many parts of the United States and overseas theaters. Detailed investigations of a number of these outbreaks are described in special reports from members of the Commission on Influenza to The Surgeon General, United States Army. However, it is of interest and importance to indicate the time, location, and extreme variability of these widely scattered upsurges of the disease which were identified by virus isolation or by serologic evidence.
35 Essential Technical Medical Data, Caribbean Defense Command, 20 Feb. 1945.
The earliest outbreak occurred in March at Sioux Falls, although the serologic evidence of influenza B was not obtained until after the virus had been identified by Dr. J. E. Salk in sharp outbreaks at Buckley and Lowry Fields, Colo., in May. Streptococcal infection was also high. Evidence pointed to the fact that influenza was present, too, in the neighboring civilian population of Colorado as a very mild illness, not recognized clinically as influenza. Serologic. studies at this same time in a hospital ward for respiratory illnesses at Sheppard Field, Tex., demonstrated that influenza B was present although its nature had not been suspected clinically. In April, a flurry was identified serologically at Fort Lewis, Wash., by the Ninth Service Command Laboratory. A sharp civilian outbreak in the town of Kasson, Minn., was recognized only in the school children, 80 percent of whom were affected; the peak was in the middle of May. Tests with sera from patients convalescent from an outbreak in Alaska in May demonstrated influenza B.
In June and July, sharp outbreaks occurred in the prisoner-of-war camps at Camp Edwards, Mass., and Camp Atterbury, Ind. The Fifth Service Command Laboratory identified the Camp Atterbury outbreak. The outbreaks seemed to be limited entirely to the prisoner-of-war compounds with prevalence of 10 to 12 percent, but Dr. 'I'. P. Magill demonstrated by serologic studies that infection had been widely distributed in United States military personnel at Camp Edwards. He suggested that the Americans were being largely immunized by subclinical infection and that the prisoner groups became more prominently affected
if they were not closely associated with United States troops. The Antilles Department laboratory reported an epidemic in San Juan beginning 8 June and reaching a peak about 22 June. In Jamaica, an estimated 50 percent of the population of Kingston were attacked in an epidemic. The disease was also identified in United States Army troops in Panama and in civilian employees in the Canal Zone. It is well to point out that Army laboratories were at this time actively engaged in the detection of the disease both by virus isolation and serologic tests.
Influenza was widely disseminated over a great part of the Pacific area. In Honolulu, a sharp civilian epidemic of 7,000 to 8,000 cases was reported by the Board of Health from 1 June to 15 July. Army admissions at this same time increased sharply with a peak on 27 June. The author and Capt. G. K. Hirst, MC, undertook an investigation at this time in the Pacific Ocean Area. Sampling of cases showed virus B was widespread. In this instance, too, streptococcal infection was prevalent without serious complications. Vaccination of essential personnel was carried out. The disease was demonstrated in naval forces at the same time, and vaccination was extended to certain specific personnel. At Tarawa in June, 83 percent of the Gilbert-Ellice labor troops were affected in an epidemic that followed the arrival of two Army ships. Caucasians in the area had little illness. Judged by admissions, little respiratory infection
occurred at Saipan and Guam, but serologic samplings showed influenza B to be prevalent. On Okinawa, serologic studies of a denguelike
disease that was prevalent among the troops showed some significant rises in titer for influenza B from 23 July to as late as 27 August.
In July, evidence accumulated of localized outbreaks in Australia 36 and British Guiana. 37 In California, influenza B was identified by Dr. M. D. Eaton in troops who became ill aboard transports from the Pacific, and, at the same time, a local outbreak was seen at Stockton Ordnance Depot.
From late August through October, influenza B was encountered at Fort Bragg, Fort Dix, Fort Lewis, and at Fort Benjamin Harrison, Ind. In October, Burnet reported both influenza A and B in Australia with a concentration of cases in young people or in country districts while troops and adult city dwellers escaped almost completely. He reported two patients with influenza from whom virus B was isolated; 10 to 12 days later, during a second attack, virus A was also isolated from those individuals.
The disease was mild during the summer of 1945 but varied from typical febrile illness of 3 to 4 days' duration, with an occasional instance of pulmonary involvement, to transient indisposition and subclinical infection. It is quite likely that in the civilian population much more of the disease was unrecognized and ignored. However, the accumulated information identified clearly a continued but shifting prevalence of influenza B during a period of 8 months. The alerted interest was thus very effective in demonstrating a peculiar, irregular blustering occurrence, rising here or there for many months. Some of the minor episodes were of considerable size but localized, yet they recurred in the same posts at intervals of months in a typical endemic-epidemic manner.
The extensive distribution of the disease was considered to indicate that a definite epidemic wave was likely in the latter part of the year. On this basis, the Commission on Influenza recommended to General Simmons, on 21 June 1945, that vaccination with influenza A and B be carried out in the entire United States Army during the month of October 1945. War Department Circular No. 267, dated 5 September 1945, instructed that the forces in all Army commands be vaccinated in October and November.
The anticipated epidemic of influenza B occurred in November and December 1945. A definite increase in respiratory admissions in the Army in the United States began in the week ending 23 November when the rate rose from 88 to 103. It rose to 148 the following week and continued to a peak of 170 in the week ending 14 December. This rise was strikingly similar in time to the onset of the 1943 epidemic of influenza A. However, the increase was not nearly so great or abrupt.
The civilian population of the United States experienced an epidemic at the same time. Reported cases rose abruptly beginning the last week in November and reached a sharp peak of 148,688 cases during the second week
36 Burnet, F. M., Stone, J. D., and Anderson, S. G.: An Epidemic of Influenza Bin Australia. Lancet 1: 807-811,1 June 1946.
37 Letter, Maj. H. G. Grady, MC, Commanding Officer, Medical Laboratory, to Brig. Gen. S. Bayne-Jones, 24 Sept. 1945, subject: Study of Influenza-Like illness in British Guiana.
in December.38They fell rapidly in the next 3 weeks to less than 50,000 cases per week. The areas most severely affected were the South Atlantic, South Central, East North Central, and Mountain States. The Pacific and New England areas, which were not affected severely, reached peaks late in December or in the first 2 weeks of January.In comparison with the 1943-44 epidemic of influenza A, the 1945-46 epidemic of type B in the general population reached a higher level for the peak week, but in total cases it was less. For the period 18 November 1945 to 26 January 1946, a total of 454,833 cases were reported ill the States where influenza is a reportable disease. For the corresponding period in 1943-44, there were 587,193 cases and in the nonepidemic year 1944-45 only 32,620 cases. In the peak week of December 1945, the State of Kentucky contributed 60 percent of the total cases while this same State contributed 18 percent in the 1943-44 peak. This report is apparently made on the basis of estimates rather than actual reported cases. If the estimates for this State were excluded for comparison purposes, the civilian incidence in 1945-46 was at least half of the 1943-44 epidemic.39
In the Army, the increase as measured by admission rates for respiratory diseases, after correction of strengths due to the number of troops on furlough during this period, remained less than 25 percent of the 1943-44 epidemic; the actual increase over the preepidemic level was so small as to give evidence of only a minor increase. The Navy admission rates were 55 percent of those in 1943-44. In attempting to evaluate the efficacy of the vaccine, a detailed study of the incidence in the Army and Navy was made. The evidence available indicated that vaccination played a considerable role in the reduction of influenza in the Army (luring the winter 1945-46. More specific studies in the comparison of ASTP units with naval and civilian students at universities are given under the vaccination studies.
In England and Western Europe, the possibility of a widespread influenza epidemic appeared as a serious threat in the fall of 1945. The shortage of fuel, the nutritional status of the population, and the continued shifting and crowding of displaced persons on the Continent appeared to set the stage for such an occurrence. In order to establish listening posts and to organize laboratories for the detection of influenza, a mission consisting of Dr. Salk, Maj. G. J. Dammin, MC, and Lt. V. Sprague, MC, was dispatched to the European theater in November 1945.40 Countrywide epidemics of mild influenza B were reported in December in Belgium and Holland.41 Sporadic cases of influenza A and B were identified in United States troops and civilians in Germany, but no general epidemic occurred. A continuous survey center for the area was established in the Fourth Medical General Laboratory. In
38 Prevalence of Disease in the United States. Pub. Health Reps. 60 and 61, July-December 1945 and January-June 1946, respectively.
39 Monthly Progress Report, ASF, War Department, 31 Dec. 1945 and 31 Mar. 1946, Section 7: Health.
40 Influenza Mission in Europe.Bull. U. S. Army M. Dept. 5: 495-496, May 1946.
41 (1) Letter, Dr. J. E. Salk and Lt. Col. G. J. Dammin, MC, to Surgeon General, 1 May 1946, subject: Report of Special Group Assigned to the Office of the Chief Surgeon, European Theater, to Assist in the Problem of Influenza During the Winter of 1945-46. (2) Dudgeon, J. A., Stuart-Harris, C. H., Andrewes, C. H., Glover, R. E., and Bradley, W. H.: Influenza B in 1945-46. Lancet 2: 627-631, 2 Nov. 1946.
England, there were few sharp outbreaks recognized, but influenza B was identified in most areas with the height of the prevalence in January 1946. As measured by an increase in deaths, the epidemic was considered moderately severe.
The Army had essentially completed its year long experience with influenza B by the end of 1945, although some extension into 1946 was noted in Europe. It is of interest, however, to note that troops, mostly from the 13th Replacement Depot in Hawaii, had a sharp increase of respiratory disease about 1 February 1946, which was identified serologically as influenza A.42 In the remainder of the Army, respiratory disease reached a point comparable to the same period of 1945, the lowest recorded level for the season (chart 13). The Army was being demobilized, and the threat of influenza which had hung over the entire period of World War II was dispelled. The experience of 1918 was not renewed, and influenza again behaved as a disease not primarily related to military conditions.
The tremendous dislocations of populations, the destruction of housing, and the rapid intermingling of people from many areas under crowded conditions was a milieu in which epidemics of typhoid fever, diphtheria, and tuberculosis rapidly gathered momentum. Circumstances were such that influenza comparable in severity to that of 1918 would be insusceptible to control. No other conclusion seems possible but that the biology of the infectious agents was the decisive factor in avoiding such an event. The studies of the disease and its prevention contributed greatly to a better understanding of its epidemiology and were responsible in a significant fashion for heightened efforts to identify and control respiratory disease of all types. There was, as always, a somewhat fatalistic attitude toward prevention or control measures, but in many situations a true effort was made to gain what benefit could be had by early institution of measures to limit crowding, to control transport of infected men, and at times to use sulfonamides prophylactically in the hope of reducing complications.
Circumstances were favorable. The periods of greatest effort were largely free from influenza or the disease was of sufficiently mild character to avoid serious disturbance. The widespread epidemic of 1943 was not prevalent in the major combat area at that time, Italy. In 1945, the European theater was essentially free from influenza B. Reports from the Pacific theater contained no significant references to influenza until 1945, with the exception of Hawaii which appears to have become a major crossroads for the transfer of influenza. Other theaters in the Far East made no reference to the disease. There is little doubt that the mild character of influenza in busy areas attracted little attention, and many were concerned with a diagnosis of influenza only if it were rapidly fatal or overwhelming. In many instances, epidemics clearly shown to be influenza, with classical clinical and epidemiologic
42 Essential Technical Medical Data, U. S. Army Forces, Pacific, February 1946.
characteristics, were called nasopharyngitis. This practice sometimes avoided additional requirements imposed by the diagnosis of influenza. The constant insistence of the
Preventive Medicine Service, Office of the Surgeon General, and its expert consultants on prompt investigation of outbreaks had left little doubt that the early distribution of information was an important factor in maintaining the alertness and interest of all commands.
RESEARCH WITH INFLUENZA VIRUS
Development of Knowledge
The lack of decisive information regarding the etiology of the pandemic disease of 1918 led to numerous efforts to establish the nature of the inciting agent of influenza. Various bacterial agents were isolated, heralded, and dismissed. Shope, in 1931,43 however, described and established the evidence that swine influenza is caused by a combined infection of virus and Hemophilus influenzae suis, with the former serving as the effective agency in dissemination and immunity. The parallelism between the characteristics of this disease in swine and influenza in men, together with an etiologic complex to mollify the bacterial and viral schools of thought, promptly opened the field to further work. At the same time, viral studies of the common cold and psittacosis were enhancing interest in respiratory diseases.
Type A virus.- In 1933, Smith, Andrewes, and Laidlaw44 isolated a virus from human cases of influenza A, which produced in ferrets, inoculated in the nose with garglings of the patients, a simple febrile upper respiratory disease of 3 to 4 days' duration involving the turbinate tissues. After recovery they were resistant
and developed in their blood antibodies which would neutralize the virus so as to prevent infection when a mixture of convalescent serum and virus was inoculated into normal ferrets. In 1934-35, the author45 Confirmed and extended those results with recovery of virus from influenza patients in many communities of the Western Hemisphere, and also in showing that, with repeated passages of these human strains in ferrets by intranasal route, the animals developed extensive, fatal viral pneumonia. Virus was established by intranasal inoculation in mice so as to produce fatal viral pneumonia. Through their use, neutralization tests for antibody were readily possible. Complement fixation tests were developed. Virus was cultivated ill tissue culture and in chick embryos.46 Subsequently, the observation by
44Smith, W., Andrewes, C. H., and Laidlaw, P. P.: A Virus Obtained From Influenza Patients.Lancet 2: 66-68, 8 July 1933.
45Francis, T., Jr.- Transmission of Influenza by a Filterable Virus.Science 80: 457-459, 16 Nov. 1934.
46 (1) Francis, T., Jr., Magill, T. P., Rickard, E. R., and Beck, M. D.: Etiological and Serological Studies in Epidemic Influenza. Am. J. Pub. Health 27: 1141-1160, November 1937. (2) Friedewald, W. F.: The Immunological Response to Influenza Virus Infection as Measured by the Complement Fixation Test. Relation of the Complement Fixing Antigen to the Virus Particle. J. Exper. Med. 78: 347-366, November 1943.
Hirst,47 and McClelland and Hare,48 that avian erythrocytes were agglutinated by influenza virus in infected allantoic fluid, added another important technique for identification of virus and serologic diagnosis. The application of these procedures to the problem of epidemic influenza became progressively established in a few years.49
It was found that, after the first years of life, a large proportion of the human population had antibodies to influenza A virus. Hence, at the onset of illness, a patient might well possess demonstrable antibodies from earlier infection, but, with recovery, a sharp rise in the level took place. It was necessary, therefore, for specific diagnosis to compare the titers of antibody in the acute phase of illness with that reached in convalescence. The specificity of the reaction was also clearly established. The serologic test thus became a procedure applicable to clinical diagnosis and to broader epidemiologic investigation in conjunction with the, isolation and identification of virus.50
Employing these procedures, it was shown that outbreaks associated with type A virus lead recurred at intervals of 2 years between 1932 and 1940-41.51 They varied widely in extent and severity; the 1936-37 epidemic was worldwide and that of 1938-39 extremely spotty and of low order, but they were both influenza A. That not all the strains of influenza A are identical was established in 1936; 52 while most strains from the same epidemic are closely similar, those from different epidemics may show distinct differences. That they are of the same type can be demonstrated by complement fixation or by hyperimmunization of animals which bring out the common type antigenicity. Under the latter circumstances, the swine strains were also seen to be related to type A strains from man. Nevertheless, another feature arose to be considered in recurrences of influenza.
Type B virus.- From the epidemic in the early months of 1940, another influenza virus, type B, (p.90) was established, and it was then possible to demonstrate that the widespread epidemic of 1935-36 was also influenza B. This virus was shown to be immunologically distinct from type A, thereby introducing a second disease, clinically and epidemiologically influenza, to be considered in the analysis of recurrences and of immunity to influenza.
No regular bacterial accompaniment
of the virus was found in the epidemic
47 Hirst, G. K.: The Agglutination of Red Cells by Allantoic Fluid of Chick Embryos Infected With Influenza Virus. Science 94: 22-23, 4 July 1941.
48 McClelland, L., and Hare, R.: The Adsorption of Influenza Virus by Red Cells and a New In Vitro Method of Measuring Antibodies for Influenza Virus. Canad. .J. Pub. Health 32: 530-538, October 1941.
49(1) Andrewes, C. H., Laidlaw, P. P., and Smith, W.: Influenza: Observations on the Recovery of Virus From Man and on the Antibody Content of Human Sera. Brit. J. Exper. Path. 16: 566-582, December 1935. (2) Francis, T., Jr., and Magill, T. P.: The Incidence of Neutralizing Antibodies for Human Influenza Virus in the Serum of Human Individuals of Different Ages. J. Exper. Med. 63: 655-668, May 1936.
50 Salk, J. E.: Laboratory Methods Used for the Recognition of Influenza. Bull. U. S. Army M. Dept. 5: 32-37, January 1946.
51 Francis, T., Jr.: Factors Conditioning Resistance to Epidemic Influenza. Harvey Lect. 37: 69-99, 1941-42. 52 (1) Magill, T. P., and Francis, T., Jr.: Antigenic Differences in Strains of Epidemic Influenza Virus: I. Cross Neutralization Tests in Mice. Brit. J. Exper. Path. 19: 273-284, October 1938.
11. Cross-Immunization Tests in Mice. Ibid.: 284-293. (2) Smith, W., and Andrewes, C. H.- Serological Races of Influenza Virus. Brit. J. Exper. Path. 19: 293-314, October 1938.
disease of man.53 Hemophilus influenzae was uncommon, but, in occasional, rapidly fatal cases with extensive destruction of the respiratory epithelium, hemolytic Staphylococcus aureus had been encountered. Thus, the evidence firmly established influenza virus as the essential infectious agent in characteristic epidemic influenza.
Antibody formation. Influenza virus produces all infection essentially limited to the respiratory tract. It has a highly selective, destructive action upon the ciliated respiratory epithelium of the nasal mucosa and upon that of the trachea and bronchi. After large doses given intraperitoneally to mice,
virus can be recovered from the lungs and, if well adapted to that species, may produce extensive pulmonary lesions. The WS strain of type A can be established ill the central nervous system of mice by the intracerebral route. Generally, however, the influenza virus can be considered rather strictly pneumotropic since, under most circumstances, inoculation of various species with active virus by other than the respiratory route elicits no evidence of infection but, circulating antibodies and resistance may ensue.
Ferrets and mice recovering from infection are commonly immune to reinoculation of the same strain of virus and also to others of the same type. This effect is not permanent for, as well demonstrated in the ferret, after a few months, even though antibodies are present in the blood, reinoculation may again cause febrile illness, with destruction of the respiratory epithelium although pulmonary lesions do not ordinarily develop. The general clinical and epidemiologic experience of man with influenza has resulted in the conclusion that immunity to the disease is of a transient nature; the evidence has always been clouded, however, by lack of knowledge of the agent involved. Nevertheless, the experimental data in man and lower animals are in accord. The fact that many of the human patients have antibodies to virus of the same type before, or at the time of, onset of influenza is clear evidence of previous experience with the agent. This knowledge, together with the, realization that there are two or more distinct types of virus and many variations of strains within the types, presents a formidable array of problems.
On the other hand, mice can be readily immunized by intraperitoneal vaccination of active or inactive virus and less readily by subcutaneous inoculation; they become resistant even after infection with virus not sufficiently well adapted to cause severe disease. Ferrets, too, can be vaccinated but usually less effectively than mice. In 1935, Francis and Magill 54 demonstrated that, virus cultivated in tissue culture can be given to man subcutaneously or
53 (1) Shope, R. E.: The Influenzas of Swine and Man. Harvey Lect. 31: 183-213, 1935-36.(2) Shope, R. E.: Swine Influenza. In Rockefeller Institute for Medical Research. Virus Diseases. Ithaca: Cornell University Press, 1943, pp. 83-109. (3) Andrewes, C. H : Immunity in Influenza. The Bearing of Recent Research Work. Proc. Roy. Soc. Med. 32: 145-152, 1939. (4) Stuart-Harris, C. H.: Influenza Epidemics and the Influenza Viruses. Brit. M. J. 1: 209-216. 251-257, February 1945. (5) Francis, T., Jr.: Influenza: Methods of Study and Control.Bull. New York Acad. Med. 21: 337-355, July 1945. (6) Burnet, F. M., and Clark, E.: Influenza.A Survey of the Last Fifty Years in the Light of Modern Work on the Virus of Epidemic Influenza.Monographs from the Walter and Eliza Hall Institute of Research in Pathology and Medicine, No. 4. Melbourne: Macmillan, 1942, pp. 1-118.
54 Francis, T , .Jr., and Magill, T. P.: Cultivation of Human Influenza Virus in Artificial Medium. Science 82: 353-354, 11 Oct. 1935.
intracutaneously without eliciting signs of infection but resulting in the development of antibodies which reach a peak in about, 14 days and are maintained for months. The levels attained, the curve of development, and the persistence are quite parallel to those observed in subjects undergoing the actual disease; hence, if immunity in man is correlated with antibodies as it is in other animals, the results of vaccination strongly suggest that resistance in man could be similarly effected. In this background of information lay a basis for efforts toward prophylactic immunization. Before the advent of the Commission on Influenza, different investigators had undertaken further studies of vaccination with preparations of virus from tissue culture, mouse lung, and chick embryo.55 In each instance, vaccination had resulted in antibody formation, but the protective value against the disease had not been clearly established; nevertheless, some of the results had suggested a beneficial effect.
Organization for Researchin War Period
The onset of war in Europe met in the United States a firm commitment of neutrality. However, with the progressive victories of the German armies, it became apparent that American democracy must be prepared for its own defense. Preparation meant more than the induction of men and the manufacture of materials. It meant the creation of forces trained in advance and maintained in a state of effectiveness. No longer did events await the arrival and the preparation of volunteers in the numbers now required. Manpower was important.
It is commonly said that the medical knowledge of one war has usually been forgotten and bitterly relearned in the next. The microbial enemy has often been more destructive than lead and steel. Certainly it is true that personal courage and indifference to risk have frequently been the substitute for sanitary and other preventive measures. But preparedness is medical too. In this instance, the history of respiratory disease in World War I in a nastily mobilized army without adequate provision for mass phenomena of disease had left its memory. The improvised efforts to meet a terrible situation had been splendid, but they emphasized the need to view the possible problems in ad-
55 (1) Stokes, J., Jr., McGuinness, A. C., Langner, P. H., Jr., and Shaw, D. R.: Vaccination Against Epidemic Influenza With Active Virus of Human Influenza. Am. J. M. Sc. 194: 757-768, December 1937. (2) Smorodintseff, A. A., Tushinsky, M. D., Drobyshevskaya, A. I., Korovin, A. A., and Osetroff, A. I.: Investigation on Volunteers Infected With the Influenza Virus. Am. J. M. Sc. 194: 159-170, August 1937. (3) Martin, W. P., and Eaton, M. D.: Experiments on Immunization of Human Beings Against Influenza A. Proc. Soc. Exper. Biol. & Med. 47: 405-409, May June 1941. (4) Horsfall, F. L., Jr., Lennette, E. H., Rickard, E. R., and Hirst, G. K.: Studies on the Efficacy of a Complex Vaccine Against Influenza A. Pub. Health Rep. 56: 1863-1875, 19 Sept. 1941. (5) Dalldorf, G., Whitney, E., and Ruskin, A.: A Controlled Clinical Test of Influenza A Vaccine. J. A. M. A. 116: 2574-2577, 7 June 1941. (6) Brown, J. W., Eaton, M. D., Meiklejobn, G., Lagen, J. B., and Kerr, W. J.: An Epidemic of Influenza.Results of Prophylactic Inoculation of a Complex Influenza A-Distemper Vaccine. J. Clin. Investigation 20:663-669, November 1941. (7) Stuart Harris, C. H., Smith. W., and Andrewes, C. H.: The Influenza Epidemic of January-March, 1939.Lancet 1: 205-211, 3 Feb. 1940. (8) Taylor, R. M., and Dreguss, M.: An Experiment in Immunization Against Influenza With a Formalde hyde-Inactivated Virus. Am. J. Hyg. 31: 31-35 (see. B), January 1940. (9) Siegel, M., Muckenfuss, R. S., Schaeffer, M., Wilcox, H. L., and Leider, A. G.: A Study in Active Immunization Against Epidemic Influenza and Pneumococcus Pneumonia at Letchworth Village. IV. Results in an Epidemic of Influenza A in 1940-41. Am. J. Hyg. 35: 186-230, March 1942.
FIGURE 2.-Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army. Front row, left to right: Col. (later Brig. Gen.) J. S. Simmons, Dr. O. H. Perry Pepper, Dr. A. J. Warren, Dr. E. W. Goodpasture, Dr. F. G. Blake, Dr. O. T. Avery, Dr. K. F. Maxey, Dr. A. It,. Dochez, and Lt. Col. (later Brig. Gen.) S. Bayne-Jones. Second row, left to right: Dr. J. R. Paul, Dr. P. H. Long, Dr. C. M. MacLeod, Dr. T. Francis, Jr., Dr. W. A. Sawyer, Dr. J. Stokes, Jr., Dr. O. H. Robertson, and Dr. M. H. Dawson.
From the start, emphasis was placed on a broad program of study of
epidemics and of control measures as shown by the initial outline
presented by the Commission on Influenza to the Board on 27 and 28
antibody titers at intervals after vaccination
TABLE 22.-Summary of
clinical evaluation of vaccination against
influenza, 1943 (combined totals of all results)
is of importance in estimating the immunizing effect of either vaccine
or of the natural infection. There was a definite trend indicating the
tendency for the highest frequency of disease to occur in that portion
of the vaccinated population with the lowest antibody titers; the same
relation existed in the unvaccinated population. There were suggestions
that this correlation was more distinct when antibodies were measured
against strains from the epidemic rather than against the PR8 strain of
for influenza in vaccinated Army units and unvaccinated Navy units at
the University of Michigan and at Yale University over an