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Albert B. Sabin, M.D.
In the United States, the interest of military medicine in poliomyelitis is not related to the relatively small number of individuals of Army age who are rendered noneffective by this disease, although it is noteworthy that residuals of poliomyelitis have been responsible for rejection of nearly one percent of the men found unfit for military duty by induction boards during World War II.1 However, poliomyelitis presents special problems not only to the medical officers who are concerned with the management of patients but also to those who are concerned with the public health measures and morale of military installations. Since other infectious diseases of human origin which occur predominantly in childhood are special problems during periods of mobilization when millions of young men are brought together from different surroundings into a life of intimate association, the military epidemiologist is naturally concerned with the behavior of poliomyelitis under these conditions. During World War II, large numbers of Americans were thrown into contact with populations living under primitive sanitary conditions, which often deteriorated still further under the effects of combat, and the appearance of poliomyelitis under these circumstances presented intriguing questions to the military epidemiologist and unexpected problems to medical installations in far-off places.
World War I.-During the period 1917-19, poliomyelitis in the United States was still predominantly, if not exclusively, a disease of early childhood. The number of individuals of Army age affected by poliomyelitis during epidemics of the disease was of a very low order. Among enlisted men in the United States and Europe, during the period 1 April 1917-31 December 1919, there were 81 cases of poliomyelitis, and it is noteworthy that the incidence rate was approximately 2 per year per 100,000 average strength, for an average strength of 1,346,615. There were no admissions among officers and probably very few, if any, secondary diagnoses of poliomyelitis other than those among enlisted personnel in the United States and Europe during the period.
This low incidence suggested that poliomyelitis did not behave like the other diseases of childhood such as measles and mumps, which frequently appear in epidemic form among new recruits. While it was thus evident that poliomyelitis behaved differently from the diseases of childhood, which are known to be transmitted by droplet infection, it was not clear whether a different mode of viral dissemination or an inherent resistance of individuals of Army age was the responsible factor. There were 5 deaths among the 81 enlisted men in the United States and Europe who incurred the disease, yielding a case fatality rate of only 6.17 percent, a figure which makes an interesting comparison with the "virulence" of certain outbreaks during World War II.
Period between the World Wars.-The number of cases listed in the Annual Reports of The Surgeon General, U.S. Army, during the period 1920-41 are shown in table 38. It is of interest to examine separately the data for the troops in the continental United States and those for troops stationed overseas. In the continental United States, the attack rate for any one year did not exceed 3 per 100,000, and there were some years in which no cases of poliomyelitis were recorded. The mean annual attack rate for the 5-year period 1935-39 is 1.4 per 100,000, which is not significantly different from that observed in the much larger numbers of individuals during World War I. Furthermore, the 4 cases of poliomyelitis which occurred during this 5-year period in U.S. troops overseas were distributed as follows: 2 in the Philippine Islands (1936, 1939); 1 in China (1937); and 1 in Hawaii (1939).
Observations in the Philippine Islands.-Of particular interest to military preventive medicine, especially in view of what happened subsequently during World War II in the Philippine Islands, is an account by Lt. Col. (later Brig. Gen.) Charles C. Hillman, MC,2 of an outbreak which occurred in 1934. Seventeen cases of poliomyelitis were admitted to the Sternberg General Hospital, Manila, Philippine Islands, in 1934. Of the 17 cases, 3 (the 3 recorded in the 1935 Annual Report of The Surgeon General) were in military personnel and the remaining 14 were in dependents of military personnel. Colonel Hillman noted that a very interesting feature of the disease was its social and racial distribution in the Philippine Islands. He stressed that all of the 17 patients had enjoyed superior environmental and nutritional advantages. The 3 military cases were among enlisted men, but 2 of these cases were in noncommissioned officers. Of the 14 cases among dependents, 12 occurred in families of officers and 2 in families of noncommissioned officers. One of the patients was the infant daughter of a Philippine Scout officer; otherwise, all were Americans. None of them were recent arrivals from the United States. Two of the cases occurred in the families of medical officers on duty in Manila, one case in the wife of a ward officer who attended most of the patients with poliomyelitis at the Sternberg General Hospital. Except for two cases that came from Nichols
Field, the number of admissions from Fort McKinley and the number from the post at Manila were about equal. Aside from the two cases which occurred in the medical officers' families, there was no known direct or indirect contact between the cases. One group of four cases which occurred in succession in another officer's family may have acquired the infection from a common source.
In addition to these cases of poliomyelitis which occurred in military personnel or their dependents, 12 other cases of poliomyelitis were reported to the Philippine Health Department during 1934 from the whole Philippine Archipelago. Nine of these were reported from the civilian population of Manila and three from the neighboring provinces of Laguna and Rizal. It is of interest to quote from Hillman's communication:
Of the 12 civilian cases, four were Americans (in three families), one was a mestizo, and seven were Filipinos. Considering the vast preponderance of native to American born it will be observed that the incidence rate, even in the civilian population, was
much greater for Americans than for Filipinos. The epidemiological factors that account for this relatively high incidence among Americans, at three separate military stations and in the civilian population, remain a mystery.
With the more limited knowledge of the human disease which obtained in 1934, Colonel Hillman did not even consider the possibility that inapparently infected Filipino domestic servants might have been responsible for bringing the infection to the families of the American officers and the civilians. His speculations, however, included the following: "Assuming that the intestinal tract is the usual portal of entry of the virus into the system, the high incidence and scattered distribution of cases among officers' families, may logically be attributed to some infected food product imported from the States and used largely by commissioned personnel." This speculation is of interest because, during World War II, there were also those who initially were inclined to attribute the unexpected number of cases of poliomyelitis among American personnel in the Philippine Islands to importation of the virus from the United States.
KNOWLEDGE OF THE DISEASE AND CONTROL MEASURES
The year 1939 perhaps marks the end of a decade during which the predominant concept of the nature of human poliomyelitis was that the infection entered and left by way of the nose. It was believed, on the basis of animal experiments, that from the nose the virus entered the central nervous system by way of the olfactory mucosa and pathways to produce the ultimate changes in the central nervous system which gave rise to the characteristic manifestations of the disease. According to this view, droplets emanating from the noses of people with the infection constituted the chief source of the infectious agent. When the methods of chemical prophylaxis, which proved so successful in the prevention of the experimental poliomyelitis in monkeys resulting from nasal instillation of the virus, were found to be without effect in human beings, considerable doubt arose that this was indeed the mode of infection occurring in human beings.
Subsequently, it was demonstrated that the feces of patients with either paralytic or nonparalytic poliomyelitis constituted a rich source of the virus; that both the virus and the lesions which were so constantly present in the olfactory bulbs of monkeys and chimpanzees infected by the nasal route were absent in the olfactory bulbs of human poliomyelitis patients; that the whole alimentary tract including the throat was indeed a place where the virus was present not only in the contents but also in the washed tissues; and that under controlled conditions the virus was regularly absent from the nasal mucosa, salivary glands, and saliva. All these observations led to the consideration of the alimentary tract as an important system as regards both entry and exit of the virus. This concept was strengthened by the demonstration that with certain strains of the virus of recent human origin it was possible to produce poliomyelitis in cynomolgus monkeys as well as in
chimpanzees by feeding the virus under conditions which definitely eliminated infection by the olfactory pathway. As a further natural consequence of these developments, it was found that the filth flies were abundantly contaminated with virus not only when they were trapped near privies in rural areas but also during epidemic periods in cities in regions where no open privies were in evidence. Thus, it became obvious that, while the relative importance of different modes of infection might vary under different conditions, it was necessary to consider all of the various ways by which human excreta, potentially infected with the virus of poliomyelitis, might reach other human beings. Although virus had been demonstrated in the throat, there was no evidence that it appeared in the oral secretions under ordinary circumstances.3
Recommendations Regarding Control Measures
During the summer of 1941, the Commission on Neurotropic Virus Diseases of the Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army (Army Epidemiological Board) prepared for the Preventive Medicine Service the following statement and recommendations:
A. General Statements-Virus and Feces in Sewage
1. It is now abundantly clear that poliomyelitis virus is common in the stools of paralytic and abortive cases of the disease and that during epidemics the virus may be transported a number of miles in sewage.
2. It is of practical importance that during even small outbreaks of paralysis there may be large numbers of abortive cases which furnish an important group of apparently healthy or convalescent intestinal carriers of the virus.
3. Carriers of the virus are more numerous among children than among adolescents or adults. Accordingly, the civilian population is to be considered as a greater potential source of virus than the military.
1. Keep a graphic record of the occurrence of cases of poliomyelitis in the civilian population, according to counties in the neighborhood of military areas.
2. When poliomyelitis is nearby, prohibit the military personnel from swimming in civilian pools or in any waters contaminated with civilian wastes.
3. Make sanitary inspections of infected civilian areas for unscreened or unsuitable privies or privies built on unsuitable soil, and for unsatisfactory sewage disposal.
Again, in 1943, at the request of the Chief, Preventive Medicine Service, Office of the Surgeon General, the Division of Medical Sciences of the National Research Council sponsored a discussion by outstanding authorities in the field of poliomyelitis which resulted in a number of recommendations including the following:
1. Medical aseptic technique is to be carried out for a minimum of three weeks from the onset of the febrile stage of the disease. Increased attention should be given to the measures prescribed in A.R. 40-210, concerning procedures to be followed in epidemics of
gastrointestinal or respiratory disease including reduction of contact between individuals, hospitalization of suspects and patients, and the application of rigid "typhoid precautions" to hospitalized personnel.* * * * * *
3. Tonsillectomies should not be performed during a period of increased prevalence of poliomyelitis.
4. Swimming in water which may be polluted by respiratory or intestinal discharges should be sharply limited when poliomyelitis is prevalent in the area.
It was apparent, however, that a general discussion of preventive measures showed no unanimity of opinion about the likelihood of diminishing the case rate by any practicable measures for isolation of cases or contacts. The opinion was expressed that there is no available way to identify healthy carriers who harbor the virus in the alimentary tract, and without such identification it is impossible to affect the spread of the disease by restrictions on patients and contacts.4
Certain important recommendations with regard to the general management of military patients were also made at the conference. Among these recommendations were the following:
1. This conference recommends that in the Armed Forces patients with poliomyelitis should be treated at the nearest available hospital during the acute stage of the disease. It is felt that transportation of the patient during this phase of the illness is hazardous. If special equipment such as a respirator is needed, the equipment should be carried to the patient rather than moving the patient to the equipment.
2. In the opinion of this Conference there is no well established evidence that any special form of local treatment is specifically curative or affects the ultimate outcome or extent of the paralysis.
3. The preponderance of available evidence does not indicate that the use of convalescent serum in treatment of poliomyelitis is efficacious.
Circular Letter No. 175, Office of the Surgeon General, U.S. Army, dealing with the management of poliomyelitis was issued on 20 October 1943 and embodied the basic principles which appeared most reasonable at that time.
EXPERIENCE DURING WORLD WAR II
There are two sources of data from which statistics on the incidence of poliomyelitis in the Army have been derived: (1) The periodic statistical health reports which contain predominantly preliminary or tentative diagnoses and (2) the individual medical records which contain the final diagnosis. The periodic statistical health reports suffer from the fact that the tentative diagnosis is not infrequently different from the final diagnosis, while the individual medical record data are derived from sample tabulations
and are subject to a certain degree of sampling error. The differences in the statistics for poliomyelitis derived from the two sources for the years 1942-45 are shown in table 39. It may be seen that in 1942 and 1943 the analysis of individual medical records for the total Army as well as for the Army in the United States produced more cases of poliomyelitis than the periodic statistical health reports, while in 1944 and 1945 the reverse was true. Since there is no satisfactory explanation for this discrepancy, it may be well to allow a very large margin of error in utilizing these statistics. Incidence data based on preliminary sample tabulations of the individual medical records for 1940-41 are shown in table 38, and data for 1942-45 in table 40.
Data contained in individual medical records and statistical health reports corroborate the impressions of individual observers to the following extent:
1. Poliomyelitis was more frequent in the U.S. Army in the continental United States than in Europe. Only in 1942 was the rate higher in Europe, but the difference was not statistically significant.
2. Poliomyelitis was more frequent in U.S. Army Forces in the Middle East (and Near East), China-Burma-India, and Philippine areas than in other oversea areas and continental United States.
3. Poliomyelitis was rare, or did not occur, in U.S. Army Forces in the Southwest Pacific except in the Philippines, where a surprisingly large number of cases occurred.
The mean annual incidence rate (0.034 per 1,000) for the Army forces in the continental United States during the 6-year period 1940-45 was approximately 2 or 3 times higher than that which obtained during the 5-year period 1935-39, and about one-third higher than the rate which prevailed during World War I. While this may represent, in part, the somewhat greater morbidity in higher age groups in recent years, it is also possible that the greater frequency with which cases of aseptic meningitis were diagnosed as poliomyelitis (nonparalytic) during World War II might also have contributed to this difference. Another possibility is that, while the data for World War I cover a period of only 2 years, those for World War II cover a period of 6 years, and it is well known that the incidence of poliomyelitis can vary not only from year to year but also from decade to decade.5
It seems highly desirable to know to what extent, if any, the conditions of military life in the continental United States may affect the incidence of poliomyelitis in individuals of Army age. Since the usual statistics on the morbidity rates of poliomyelitis among civilians do not contain data for the age groups which make up the bulk of the Armed Forces, data were obtained for civilian residents of the cities of Cincinnati and Cleveland, Ohio, for
certain years of the 1940 decade (tables 41 and 42). Although these data on the morbidity rates of poliomyelitis among civilians of Army age are obviously not representative of the entire United States, it is, nevertheless, interesting that these rates are of the same order of magnitude as those encountered in the Army in the United States and Europe. This would suggest, as did the experience of World War I, that the conditions of Army life in the United States and Europe do not lead to an increase in the incidence of poliomyelitis.
by Dr. Eugene Wehr and Mr. I. G. Schneider, Bureau of Vital Statistics,
Cincinnati Health Department, and Mr. Floyd Allen, Public Health Federation
1From data reported by Dehn, H. M.: The Age Incidence of Poliomyelitis in Cleveland. Pediatrics 1: 83-89, January 1948.
The poliomyelitis morbidity rates shown in table 40 for U.S. Army Forces in the Middle East and the China-Burma-India theaters are greatly diluted by calculations based on average strengths per annum and do not properly portray, the problems which were encountered by specific units living under certain conditions at certain times. Accordingly, it appears desirable to analyze particular poliomyelitis experiences both in the United
States and abroad in order to obtain some idea of the conditions which predisposed to increases in the incidence of this disease.
Outbreaks in the Continental United States
Perhaps the most important fact about the vast majority of the cases of poliomyelitis in the Army in the United States and Europe is that they were isolated and sporadic and, with the few exceptions to be described, did not result in outbreaks among the units in which they occurred. It may be of interest, from the point of view of military preventive medicine, to examine the few outbreaks of poliomyelitis which did occur in military installations in the United States during World War II, to determine whether or not any lesson may be learned regarding the natural history of such outbreaks and their management.
San Antonio, Tex., 1942
Late in December 1942, the Commission on Neurotropic Virus Diseases was called upon to investigate a poliomyelitis epidemic which occurred in the civilian population of San Antonio, Tex., the location of Fort Sam Houston. It was a late epidemic, by northern standards, since it started in September and reached its peak in November, with cases continuing to occur in December and January of 1943. By the end of December, about 75 cases, including 5 deaths, had been listed in the city and its immediately surrounding territory. Although only 3 cases, one of them fatal, occurred in soldiers, there were a number of cases among the families of officers and men posted in that area. Eleven patients, mostly juvenile members of the families of officers and men living on the post area or its general vicinity, were admitted to the Brooke General Hospital at Fort Sam Houston. Dr. John R. Paul, who investigated this epidemic, was impressed by the manner in which poliomyelitis indirectly becomes a military problem when it appears in the families of military personnel living on a military post. No data are available to indicate whether or not the incidence of the disease was higher among military families than among comparable groups in the population at large. Dr. Paul remarked:
The opportunity of measuring the incubation period was present in several instances in which children contracted poliomyelitis shortly after their arrival in San Antonio. In most instances this occurred in the families of soldiers recently transferred from areas in which there was no reason to suspect that poliomyelitis had been epidemic. In one child, the onset of the disease began five days after her arrival in the city.
The lesson that one might learn from this experience is that it would appear to be advisable to postpone the movement of children of military personnel into military installations situated in areas in which an epidemic of poliomyelitis is in progress. Although this outbreak might fall into the category of a "winter epidemic" by northern standards, it cannot be so regarded for a southern city such as San Antonio, where the temperature was 60° F. or
higher during most of the period of the outbreak. Poliomyelitis virus was recovered from flies which were collected on 29 and 30 December from one home where two cases of poliomyelitis had developed in mid-November.
Pasadena STAR Unit, 1943
The outbreak of poliomyelitis which occurred in the Pasadena STAR (Special Training and Reassignment) unit in August 1943 is of some interest as an example of the occasional high attack rate in a relatively small group of men under circumstances suggesting not only a common source of infection but also acquisition of the infection during a limited period of time. The STAR unit at Pasadena College, Pasadena, Calif., consisted of approximately 800 men. On 14 August 1943, at a time when no clinical poliomyelitis was recognized in the group, 310 men left for duty at Indiana University, Bloomington, Ind. One of these men, who was slightly ill at the time of departure, developed signs of bulbar poliomyelitis en route and was removed from the train in Colorado, where he died on 18 August.6 When the group arrived in Indiana, one additional man had paralytic poliomyelitis, although he too had signs of illness on 14 August. Of the 309 men who got to Bloomington, 16 developed signs and symptoms compatible with the diagnosis of paralytic or nonparalytic poliomyelitis during the few days immediately following their arrival. No paralytic cases occurred with onset after 19 August, and in 5 of the 8 men who were reported to have nonparalytic poliomyelitis with onset between 22 and 25 August the diagnosis may be in doubt because the clinical manifestations in these individuals were not associated with any abnormal changes in the cerebrospinal fluid.7 It is not improbable, however, that even these doubtful cases may represent instances of infection with the poliomyelitis virus, although there is no way of being certain. Shortly after arrival, these men and their contacts were quarantined in separate quarters and were kept in complete isolation for a period not stated in the records. No further cases occurred in this quarantined group or their contacts after the first few days following their arrival, and no cases occurred among the other units on the campus of Indiana University.
Among the men of this unit remaining in Pasadena College, one developed paralytic poliomyelitis with onset on 15 August and another with onset on 20 August. Although the group in Pasadena was quarantined and observed, there is no record of nonparalytic poliomyelitis or other minor illness among them. Furthermore, another man from this unit who was transferred to Camp Santa Anita, Los Angeles County, Calif., on or about 14 August developed paralytic poliomyelitis with onset on 18 August. (Available rec‑
ords do not indicate whether he was the only one transferred to Camp Santa Anita from the Pasadena STAR unit or whether others were also sent there.) Seven cases of paralytic poliomyelitis occurred between 14 and 19 August among this group of between 700 and 800 men, giving a paralytic attack rate of approximately 1 percent. If one also includes the 12 possible nonparalytic cases which occurred among the group entrained for Bloomington, the total attack rate would appear to be 2 percent. The brevity of the period during which the paralytic cases had their onset suggests not only a common source of infection but also that this common source was somewhere and somehow connected with the life of this unit at Pasadena and that the infection was acquired during a relatively short period of time.
In reply to a number of specific questions from Col. (later Brig. Gen.) Stanhope Bayne-Jones, MC, then Assistant Director, Preventive Medicine Division, Office of the Surgeon General, the contract surgeon of the unit, Dr. F. C. Hargrave, supplied information which might be of importance in relation to this outbreak. Some of the interesting points in the history of this unit are as follows:
1. During the 6 weeks before the outbreak of poliomyelitis there were two outbreaks of diarrhea which were unexplained on the basis of food or illness in foodhandlers or other demonstrable factors. The first occurred on 2 July, and at that time 259 of the 838 men were affected. The second episode of diarrhea occurred on 23 July, and 242 of the 782 men were affected.
2. The surgeon reported that there was no increase in flies but that he had battled them all summer.
3. Apparently, the use of the swimming pool was compulsory, and the monthly sanitary report for July 1943 stated: "The incidence of nasopharyngeal infection has remained about the same but quite a few have developed either otitis media or otitis externa as a complication." The monthly sanitary report for August 1943 stated: "The incidence of nasopharyngeal infection has been reduced by almost one third and is accompanied by very few complications." The swimming pool was closed on 16 August when the first clinical diagnosis of poliomyelitis was made.
4. There were no changes in messhall personnel, but one new dishwasher arrived on 8 August 1943.
It is extremely interesting that the first cases of poliomyelitis appeared within 6 days after the new dishwasher was taken on. The distribution of the incubation period suggests that all the patients probably acquired their infection at the same time, and the high attack rate suggests that the virus must have been abundant. In view of episodes which occurred elsewhere and which will be described later, one must consider the possibility that the infection may have been acquired from contaminated food or utensils. One can only speculate whether this contamination occurred by means of a single carrier such as might be represented by the newly employed dishwasher or whether the mechanism which was responsible for the two earlier episodes
of extensive diarrhea within the unit might have on this particular occasion been responsible for the dissemination of the heavy dose of poliomyelitis virus. At any rate, it is noteworthy that no cases of poliomyelitis occurred among those who left this unit at the end of July or early August and that no additional cases of poliomyelitis occurred at Pasadena College during 1943 among those who came after the quarantine was lifted. In addition, the introduction of the 309 men to Bloomington, even though they were quarantined rather soon after their arrival, did not result in the appearance of poliomyelitis among the civilian and military personnel associated with this group. Of course it is not possible to predict what might have happened if these men had not been quarantined as efficiently as they were within a short time after arrival in Indiana.
For comparison with the events in the STAR unit in Pasadena, it is of interest to observe happenings among similar units in other schools in the Ninth Service Command, as well as in certain other service commands. The ASTP (Army Specialized Training Program) unit of the University of California at Los Angeles reported two cases of poliomyelitis, one with onset on 27 May 1943 and the other with onset on 18 August 1943. The ASTP unit of the University of Oregon, Eugene, Oreg., also reported two cases, one with onset on 10 September 1943 and the other with onset on 26 September 1943. The Sixth Service Command reported that as of 24 September 1943 there had been no cases of poliomyelitis reported from any ASTP or STAR unit within that service command since 1 January 1943. The Fifth Service Command, in which Indiana University is located, reported on 22 October 1943 that, aside from the cases which occurred in the group transferred from Pasadena College, there had been none reported since 1 January 1943. All of this merely testified to the uniqueness of the outbreak which occurred at the Pasadena College.
Fort McClellan, Ala., 1945
The epidemic which occurred at Fort McClellan in March and April 1945 is the only example of an outbreak of poliomyelitis in an isolated Army camp in continental United States. This epidemic which presented many interesting and unique features was studied by Dr. Robert Ward and Dr. John R. Paul of the Commission on Neurotropic Virus Diseases, and the laboratory work connected with this investigation was carried out with the assistance of Dr. J. L. Melnick at the Yale University School of Medicine, New Haven, Conn. The description which follows is based upon the data presented in the report of these investigators.
Fort McClellan was a large camp situated in northeastern Alabama 6 miles north of Anniston in hilly, forested country. It was predominantly an infantry replacement training center and in March 1945 had a complement of about 30,000 men, most of whom were recent recruits. Seventeen cases of
poliomyelitis, all of them paralytic, occurred within a very brief period of time (February 25 to April 15) yielding a paralytic attack rate of approximately 0.57 per 1,000 men. All the cases were in soldiers. No families or children were involved. The available data on the ages of 16 of the patients indicate that all but 4 were 18 or 19 years of age; 2 were 21; 1 was 25; and 1 was 33 years of age. Ten of the seventeen patients presented bulbar symptoms and three of these patients died yielding a total case fatality of 18 percent. It is striking that, although a thorough search was made, the diagnosis of nonparalytic poliomyelitis was not established in a single case. The first case was recognized only in retrospect. The patient presented himself with weakness of the arms on 1 March 1945, and because his weakness was not at the time associated with fever his illness was not regarded as poliomyelitis, although it was subsequently discovered that he had suffered from a minor illness diagnosed as "nasopharyngitis" on 25 February 1945. The evidence, of course, is not incontrovertible that the diagnosis in this patient was poliomyelitis.
During the period between 25 February 1945, when the onset of the first potential case occurred, and 21 March, when the definite cases began, there were no other cases of the disease. However, between 21 and 28 March, 10 of the subsequent 16 cases occurred. The explosive character of this outbreak strongly suggests again, as in the case of the Pasadena STAR unit, that these infections were acquired almost simultaneously from some common source that happened to be rich in virus, to which a large number of this relatively resistant population of older age group individuals must have been exposed at one time. While the subsequent cases may represent instances of longer incubation periods, it is also possible that at least some of them may represent instances of secondary infection. It is of especial interest, therefore, that an investigation revealed no possible contacts among the cases. Not one patient knew another patient. Of the 17 patients, 2 were in one company and 2 in another company. The remainder of the 17 were scattered throughout the camp. There was no common eating place for all. The interval of approximately 4 weeks between the onset of the first case (assuming that the patient who became ill on 25 February was indeed a case of poliomyelitis) and the subsequent sharp outbreak makes it rather unlikely that he and other undiagnosed cases or carriers were responsible for the "silent" spread of virus throughout the camp which finally resulted in an explosive outbreak consisting entirely of paralytic cases.
The precise determination of which of the various possible modes of spread of the poliomyelitis virus might have been responsible for this unusual outbreak presents almost insurmountable difficulties owing to the inadequacy of the methods available for the detection of virus in various materials and carriers. Poliomyelitis virus was recovered from only one of the three patients with fatal cases, whose central nervous system tissue was tested in
monkeys. Similar tests in monkeys on water, milk, ice cream, flies, and sludge yielded negative results.
In reviewing the data on this outbreak, one is strongly impressed with the possibility that some temporary factor peculiar to this camp might have been responsible for this unusual epidemic. During the month of March when the majority of the cases occurred in the camp, only one other case of poliomyelitis was reported for the entire State of Alabama. Although another case of "poliomyelitis," reported from Camp Sibert, Ala., about 40 miles distant, with a complement of 3,500 men, suggested the possibility that something distributed in common to both camps might have carried a great deal of virus, one cannot be certain of the diagnosis in the patient at Camp Sibert because he presented only the aseptic meningitis syndrome which may or may not have been due to infection with the virus of poliomyelitis. The temperature during March when the epidemic occurred was said to have been unusually warm, almost approaching that of summer weather. Although flies were not yet abundant, the investigators had no difficulty in securing specimens outside five company messes where patients had taken their meals a week or 10 days before. Other observations of interest include the fact that the camp had its own sewage disposal plant located about half a mile from the nearest barracks. The sludge from this plant was dried in beds and then used as fertilizer for the flower gardens on the post. This practice was stopped at the beginning of the epidemic. Although the milk was pasteurized, the investigators found that the sanitary conditions under which the milk was produced were not of the best, and that one of the subproducers had recently been cut off because the prepasteurization bacterial count was very high. Some of the subproducers sent their entire milk supply to the Army camp. Other subproducers divided their milk between the Army camp and the adjacent town of Anniston, in which no cases of poliomyelitis had been detected. The food was procured almost entirely through Army depots which supplied many other Army camps in which no cases of poliomyelitis had occurred. When the investigators inspected the handling of the butter from the quartermaster depot, they were impressed by the number of persons who made contact with this butter which had been manufactured elsewhere. It is, of course, not inconceivable that a healthy carrier working at the quartermaster depot could have contaminated large amounts of butter which was then distributed simultaneously throughout the camp. It is, furthermore, of interest that during March 1945 (the month of highest incidence of poliomyelitis) over 5,000 teeth were extracted at the post, but none from the individuals who developed poliomyelitis. One of the persons with a fatal case of bulbar poliomyelitis had had two impacted teeth removed in December 1944-3 months before the onset of his illness. In view of the long interval, any causal relationship would seem remote.
If the appearance of occasional carriers in Army camps could set off epidemics of poliomyelitis by the many types of intimate contact which occur in such installations, it is odd that so many of the camps in which sporadic cases of poliomyelitis occurred did not have subsequent outbreaks of the disease. For this reason, the observations on the outbreak at Fort McClellan suggest that certain other factors, which have not as yet been identified, are capable of giving rise to a situation in which large numbers of men are infected within a very short period of time with poliomyelitis virus of perhaps unusual antigenic composition and virulence.
Since only two small outbreaks of poliomyelitis occurred among the millions of men in Army installations in the United States during 1940-45, it seems desirable also to analyze several outbreaks which occurred in Navy installations in the United States to supply a greater spectrum for comparison with the events which transpired in certain areas outside the continental United States. Several outbreaks of poliomyelitis which occurred at Navy installations on the West Coast were investigated by Dr. William McD. Hammon, a member of the Commission on Neurotropic Virus Diseases, Board for the Investigation and Control of Influenza and Other Epidemic Diseases in the Army, Preventive Medicine Service, Office of the Surgeon General. Two of these outbreaks were explosive and limited in time, and the epidemiological investigations indicated that the infection had occurred probably as a result of viral contamination of a widely distributed article of food.
The first of these occurred at a U.S. Naval Flight Preparatory School which was located on the campus of the California State Polytechnic College at San Luis Obispo, Calif.8 In a group of 730 officers and men, 17 cases of poliomyelitis, 9 of them paralytic, occurred, giving an attack rate of 2.3 percent. The dates of onset in 16 of these cases were all between 1 and 8 September. In view of the explosiveness of this outbreak, suggesting a common source of infection during a limited
period of time, the following epidemiological observations are of special interest:
1. The cases were rather evenly distributed among the barracks.
2. Several patients had not left the campus at any time during the 3 weeks preceding the onset of their illness.
3. Case rates of each of the four classes present during the month of August were approximately equal; a new class arriving on 2 September was not involved, although this class was present at the time of the onset of illness among the three remaining classes. The swimming pool was used almost exclusively by one class, and a number of the patients had not used it for a month.
4. All of the officers and men ate at the same mess which was operated by civilians.
5. There were about 50 civilians on the campus during the day, consisting mainly of special summer students and employees who ate elsewhere, and no recognized cases of poliomyelitis occurred in this group.
For this reason, the epidemiological study was centered on the barracks, the food and milk supply, and the messhall, and the following potentially significant observations were made:
1. Barracks erected near the school buildings were directly adjacent to areas where large numbers of domestic animals were kept. These included several thousand chickens, horses, pigs, and the dairy herd which supplied raw milk to the school mess. Manure had accumulated in very large quantities in the barns; flies were found in large numbers both in and out of buildings. Many were present in the barracks, but the numbers were very great in the messhall and the milk barn. In the toilet bowls in the barracks, flies were seen crawling over residual fecal smears. These toilet rooms all had unscreened ventilators opening outside. One toilet for the female kitchen help in the messhall was also found to have an open, unscreened window to the exterior. Each time the toilet room door was opened, flies had ready access to the kitchen.
2. Investigation of the manner in which the milk was handled suggested that if the flies on this campus were in one way or another contaminated with poliomyelitis virus, ample opportunity presented itself for contamination of the milk. Numerous flies were found on the cloth diaphragms through which the milk from the milking machines was filtered. The milk cans had been sterilized previously, but they were open and contained many live flies at the time the milk was run into them. In the messhall, flies were found crawling about in empty washed pitchers in which the milk was to be served at mealtime. All patients drank milk regularly with their meals. They claimed that dead flies were regularly found in their glasses and in the pitchers. Milk from the same sources were also served at the soda fountain, and all patients had on recent occasions had milk drinks at that fountain. It should be noted here that, following this survey and one made simultaneously by the Navy, these conditions were corrected; remedial measures included pasteurization of all milk and improved fly control.
Other factors of interest in this outbreak were that, of the 17 military cases, 3 occurred among individuals who had left this school for assignment to flying fields in Nevada, approximately 6 days before the onset of first symptoms in the cases remaining at the training school at San Luis Obispo. The exact number of men who were in the class that graduated at the end of August and left this school is not stated, although it is possible that it may represent very roughly one-quarter of the total strength in that school.
One additional case was considered as belonging to this particular outbreak. This was in a girl who was a friend of one of the graduate patients
and had attended the school commencement and who developed paralytic poliomyelitis at the same time as her friend among the graduate patients. Counting the girl's case, the total number of cases in this outbreak was 18; 10 of them were paralytic, but none were fatal. At about the same time, 100 other cadets were ill with symptoms of minor illness which could have been due to infection with poliomyelitis virus. Furthermore, among 30 graduates who went to one training field, 6 men in addition to the 2 who were paralyzed were found to have been sick and off duty at least 2 days in the second week of September with undiagnosed illnesses which, by the reported symptoms, might well have been abortive poliomyelitis. None of the other men at this field belonging to groups who had been graduated from other schools were ill during the same week. Again, it is important that, at another of the flying fields where one case of paralytic poliomyelitis occurred among the graduates who came from San Luis Obispo, there were no other cases of poliomyelitis reported during the following several weeks, either among those who came from San Luis Obispo or among other personnel. This is of particular importance, because it shows that the infection which was apparently so extensive as to cause an attack rate of 2.3 percent (not counting the minor illnesses) among those who were exposed at some particular time at San Luis Obispo failed to spread by the ordinary methods of contact in the other flying fields to which graduates of this school had gone, or as a result of the frequent visits of individuals from this school to the adjacent town.
Because the patients exhibited a rather high proportion of what were termed cerebral manifestations, such as insomnia, confusion, and irritability, encephalitis was frequently the original diagnosis. Furthermore, since the paralysis showed a predilection for the muscles supplied by the cranial nerves and the cervical levels of the spinal cord, frequently giving rise to the shoulder girdle type of paralysis, serologic tests were also carried out for Russian spring-summer encephalitis virus. However, infections with this virus, as well as with the viruses of western equine and St. Louis encephalitis, were ruled out by serologic tests. Poliomyelitis virus was isolated from the feces of three of four patients tested, and prolonged clinical studies left little doubt that the diagnosis of poliomyelitis was justified in all cases. Finally, it is worth mentioning that, approximately 10 days before the onset of the first case of poliomyelitis, there had occurred among the military personnel at the San Luis Obispo school 20 cases of an illness which was diagnosed as epidemic pleurodynia and was characterized by fever and chest pain, and it is particularly interesting that 2 of the 20 individuals with this illness later developed poliomyelitis.
The second outbreak, in which pasteurized milk contaminated during handling at the messhall was suspected as the probable common source of infection, occurred in a U.S. Naval Receiving Station at Portland, Oreg., during October and November 1944. The analysis which follows is based
upon information contained in the report of Dr. Hammon submitted to the Commission on Neurotropic Virus Diseases in 1945 and in a report published 5 years later by Lt. Comdr. Frank P. Mathews of the Naval District Epidemiological Unit.9 This outbreak occurred among 1,400 men who were billeted at this receiving station awaiting orders to board naval vessels which were under construction in the area. The station consisted of a group of five, two-storied wooden barracks, a messhall, and an office building, and it covered one city block in a partly built-up industrial section of Portland. The onsets of 11 cases of paralytic poliomyelitis occurred in this group of U.S. Navy personnel during the period 29 October-17 November. Four of the cases were in officers, and the disproportionate incidence among officers and enlisted men was a very striking phenomenon. The virus involved in this particular epidemic appears to have been one of great virulence since 4, or 36 percent, of the 11 patients died of the disease. Dr. Hammon, furthermore, pointed out that, despite a careful medical check on all persons in this installation, the diagnosis of abortive or nonparalytic poliomyelitis was considered in only 6 individuals, and most of these were also finally released without a diagnosis. There can be no question of a common source of infection for the first group of 6 cases, which included the 4 fatal cases, with onset between 29 October and 2 November. This group of 6 cases included those in all four of the officers. Since the incubation period of poliomyelitis can be quite variable, it is not improbable that the other five cases of poliomyelitis which occurred between 7 and 16 November might also have acquired their infection at the same time. However, there is a strong possibility that at least one case in this second group of five patients might represent an instance of a secondary case. This occurred in a pharmacist's mate, who, 7 to 10 days before the onset of his symptoms on 12 November, had been caring for one of the first poliomyelitis patients. During the course of his care, he had been obliged to aspirate the patient's pharynx very frequently.
An analysis of the various potential sources of infection finally narrowed itself down to a strong suspicion centering on the milk supply. While the four officer patients all lived in Portland at hotels or at home and all the patients among the enlisted men lived in the barracks, the officers, nevertheless, took their noon meal at the barracks. Since the investigation of various potential sources of infection had narrowed itself down to some article of food that might have been served uncooked or raw during the period 25-26 October (a date selected because one of the patients with onset on 1 November arrived at the station on 25 October), and since the attack rate among the officers was about 10 times higher than that among the enlisted men, the question arose as to what food had been served more generously to the officers than to the enlisted men. Mathews noted:
One outstanding such item was found to have been milk. For several months, an adequate supply of milk had not been available for the whole station. The enlisted
men had been deprived of it first. During October, the only milk served to the enlisted men had been a ladleful on the breakfast cereal. There had been none to spare for use as a beverage. On the other hand, each officer was provided with a glass of milk at his place for each of the 3 meals, instead of the customary glass of water. Furthermore, waiters refilled these glasses as they were consumed, even without waiting for a request to do so.
Although the milk and cream which were delivered daily in bulk were pasteurized, the manner of handling the milk after delivery would not have prevented its contamination by a poliomyelitis virus carrier. The milk was poured into an open dishpan for the enlisted men's breakfast, and a mess attendant scooped out a ladleful for each man's cereal. The dipper or dishpan, or both, could have been contaminated by the fingers of the dispenser. At the end of the enlisted men's breakfast, it was customary to pour the milk left in the dishpan into pitchers to furnish drinking milk in unlimited quantities to the officers for their breakfast and later meals the same day. The possibility was considered that the very much higher attack rate among officers might have been due to the fact that they had drunk so much more of the milk and, therefore, had consumed larger amounts of virus, or that the infecting event on a particular day had occurred after most of the enlisted men had already been served. It is of interest in this connection that the onset of illness was almost simultaneous in all 4 officers, and that 2 enlisted men whose onset was at the same time as that of the officers developed the disease in the most severe form and died.
A third outbreak of unusual interest occurred in 1944 among Navy V-12 trainees and civilian students at Occidental College, Los Angeles, Calif. The chief points of interest in this outbreak are not only the high attack rate, comparable to that described in previous episodes, but more especially the periodicity and grouping of the cases, as well as the fact that the outbreak remained localized among the student body without any spread to individuals or families outside the college with whom the students had abundant contact. The data reported here are taken in part from the report submitted by Dr. Hammon to the Commission on Neurotropic Virus Diseases as modified by a subsequent, personal communication from Dr. Hammon, which contained additional details.
The school was coeducational, and the student body consisted of about 800, approximately one-half civilians and one-half Navy V-12 trainees. Twenty-three cases of poliomyelitis, sixteen of them paralytic and two of them fatal, occurred in this group during the period from 9 April to 29 July. The attack rate during the semester when most of the cases occurred was 2.8 percent; since a change of term involved graduation of one group and introduction of a new one, the exposed population was somewhat greater, but only one case occurred in the new group after the vacation period which ended on 1 July. The first patient, with onset on 9 April, had an illness which was regarded as nonparalytic poliomyelitis. If the analysis of this outbreak is confined to the paralytic cases, only several distinct waves are
noted which are very closely grouped together. During the first wave, there were five patients with paralytic poliomyelitis who had their onset between 9 and 12 May. In the second wave there were three patients with paralytic poliomyelitis whose onset was between 22 and 26 May. After the vacation period, which lasted from 23 June to 1 July, four additional paralytic cases occurred with onset between 16 and 18 July, and the final group of cases with onset between 23 July and about the last of the month.
Most of the students were in residence on the campus, a few in rooms near the campus, or at home. Infections occurred in all large dormitories, in one private home adjacent to the campus, and in one nearby fraternity house. Male and female civilians and Navy students were involved in proportionate numbers. Nearly all students ate three meals on the campus in the student cafeteria, and all the poliomyelitis patients took practically all their meals there. During the period of the outbreak, there were unusually few cases of poliomyelitis reported from the rest of the city of Los Angeles, and for these no connection with the college could be traced. The activities of the students off the campus were not limited, and yet no secondary cases were traced to their visits even in families where there were children. There were many common factors in the group, which may have concerned their exposure, but all centered in life on the campus. During the various periods of apparent activity of the virus, there were several waves of increased incidence of so-called upper respiratory infection, including many cases febrile in nature, and there was one outbreak of gastrointestinal disorders. Throat cultures made by Dr. John Kessel on about 30 febrile patients during the wave of so-called upper respiratory infection showed that most had beta hemolytic streptococcal infections. Stools from most of these patients were tested either in Dr. Kessel's laboratory or in Dr. Hammon's laboratory, by monkey inoculation, but no poliomyelitis virus was isolated. Dr. Kessel did succeed in recovering one strain of poliomyelitis virus from one of the paralytic patients in whom the onset of disease occurred on 10 May.
An investigation of the possibility that some article of food consumed by the students on the college campus might have been responsible for the periodic outbreaks of the illness revealed that the practices and equipment in the dining room and kitchens were entirely adequate from a sanitary point of view. The possibility that one or more carriers of a particularly virulent strain of virus might, nevertheless, have been acting as disseminators of infection led to the testing of stools from several of the foodhandlers by Dr. Kessel, who obtained negative results. Dr. Hammon finally concluded: "All evidence points to some local factor, as of paramount interest, although a number of individual infections could be satisfactorily explained by intimate contact with a known case 7 to 10 days prior to onset. However, contact off the campus with children and non-college dates did not result in apparent infection." When one considers the limited facilities and
methods that are available for investigating such outbreaks in a search for carriers of poliomyelitis virus, it is not surprising that the local factor, although sought, was not found. The unique periodicity of this outbreak on the campus of Occidental College has a striking counterpart in an epidemic which occurred in New Zealand troops in Egypt during the period November 1940 to July 1941.10
Outbreaks in U.S. Forces Overseas
Middle East, 1943
Before the arrival of American troops in the Middle East, the British noted that the incidence of poliomyelitis in their armed forces was unexpectedly high. Van Rooyen and Morgan11 reported that in 1941 a total of 74 cases were diagnosed as acute poliomyelitis or polioencephalitis and that, of these, 19, or 26 percent, were fatal; in 1942 there were 32 cases, 14, or 44 percent, of them fatal. The attack rates for the British troops were not given. Brigadier McAlpine12 reported that the incidence per thousand of British troops in the Middle East was 0.31 in 1943 and 0.42 in 1944. This may be compared with attack rates of 0.02 per thousand for British Army forces at home during 1943 and 1944. It should be noted, however, that overall attack rates of this nature in the Middle East are frequently misleading as regards the actual incidence of the disease in a given group or force in a given period of time at a given place. Since poliomyelitis does not occur in similar numbers in different groups under different conditions of life, and since the overall attack rate is calculated on the average strength, which varied in a theater that was as mobile as that of the Middle East, one may be justified in assuming that the actual attack rate in certain forces was considerably higher than 0.3 or 0.4 per 1,000. However, whatever the statistics may be, it is evident that individuals of military age in the British forces in the Middle East had a risk of acquiring paralytic poliomyelitis which was at least 15 to 20 times greater than that of the British forces at home. Furthermore, the disease which they acquired in the Middle East was particularly virulent, and the case fatality rate was high. The work of Van Rooyen and Morgan on the recovery of many strains of poliomyelitis virus from these patients left little doubt of the diagnosis.
According to preliminary sample tabulations of individual medical records, 21 cases of poliomyelitis occurred among Americans in the Middle East theater. It was clear to the observers on the scene that the incidence of poliomyelitis among U.S. troops was proportionately about the same as
that among the British troops. The first interim report of the Commission on Neurotropic Virus Diseases in 1943 remarked on the occurrence of poliomyelitis in U.S. troops, particularly among those stationed in Libya (in the vicinity of Bengasi), in Egypt (in the neighborhood of Cairo and Alexandria), as well as in Palestine. Although many of the cases were sporadic, it was noted that two outbreaks which might be termed epidemics had been recorded with rates of between 0.5 and 1.3 per 1,000 among groups of 25,000 men. It is interesting to note in this connection that several different attack rates have now been published on the incidence of poliomyelitis in American forces in the Middle East. Paul, Havens, and Van Rooyen13 in 1944 gave the rate of 0.425 per 1,000 for the cases up to 1 October 1943. Brigadier McAlpine, writing in 1945, gave the rate of 1.4 per 1,000 for American forces in the Middle East in 1943. In a 1949 publication, Paul14 gave the rate of 0.26 per 1,000 for American troops in the Middle East in 1943. It appears that all of these rates are probably correct for certain groups, and that the lower rates represent a dilution resulting from inclusion of larger areas and forces not necessarily living under similar conditions.
Dr. Paul, who had an opportunity to observe poliomyelitis in military personnel in Egypt at first hand, made the following observation on clinical epidemiology:
Contacts and living quarters were investigated in 10 military cases of poliomyelitis or polio-encephalitis which were probably acquired in Cairo between May 1 and October 15, 1943. The cases were ubiquitous as to their place of origin. No two patients seem to have been in contact. No civilian cases were discovered among adults or children living in close proximity to the patients' living quarters. This does not mean that epidemics of poliomyelitis do not occur in the Middle East. Caughey has described an. epidemic of poliomyelitis which occurred in 1941 among New Zealand troops stationed in Egypt. Subsequently, there have been other small localized outbreaks. During the summer of 1943 there were two of these-in Libya and in Tripoli. We did not have the opportunity of examining these situations at first hand.
In an attempt to correlate these observations on the unexpected higher incidence of poliomyelitis in the British and U.S. troops in the Middle East with the occurrence of poliomyelitis in the native population, Dr. Paul made inquiries regarding the incidence of poliomyelitis in Egypt and in Palestine. Since the official statistics on the occurrence of poliomyelitis in Egypt were obviously unreliable, he inquired into the number of admissions for poliomyelitis in two children's hospitals in Cairo over a period of years from 1933 to 1942. It appeared that during that period the total number of new cases of poliomyelitis admitted each year varied from 22 to 96 during the years 1933-39 and from 110 to 201 during the years 1940-42. This constituted approximately from 2 to 12 cases of poliomyelitis for every
10,000 patients admitted to those hospitals and dispensaries per year. Furthermore, it was of interest that most of the new patients admitted for poliomyelitis were under 5 years of age. The local juvenile cases were said to have been mild usually, and severe bulbar cases were rare. The professor of pediatrics, who helped to supply these data, stated that he had seen only two cases of severe acute ascending paralysis in local children. Poliomyelitis in the native Egyptian adult seems to be rare, according to Dr. Paul, and, from verbal accounts, there were no cases observed at the military general hospital during the period of inquiry in 1943. It is, of course, obvious from this that clinical poliomyelitis is observed and does occur in native Egyptians. However, the expressions "common" or "uncommon" can hardly convey the actual attack rate and incidence of poliomyelitis in a population of 16 million Egyptians. Considering that the hospitals under investigation receive patients not only from Cairo but probably also from many thousands of people around the great metropolis, the total number of patients in the native population does not appear to the author to be large by American standards. Furthermore, it is important to remember that a city like Cairo provides a striking variety and contrast in living standards-that it represents a population of mixed racial, social, and economic groups, and may not actually reflect the incidence of the clinically apparent paralytic disease in the very poor portion, or vast majority, of the Egyptian population.
As regards Palestine, Dr. Paul quotes a study by Levy published in 1937 which again was said to indicate that poliomyelitis was not uncommon in Palestine. Actually, for the 20-year period from 1915 to 1934, the investigator was able to collect from the records of orthopedic dispensaries and physicians a series of 215 paralytic cases, or an average of 10 cases of paralytic poliomyelitis per year. Once again one must recall, in analyzing the data from Palestine, that the population there represents a very mixed group as regards living habits and standards. The Jews, both native and immigrant, have, on the whole, a living standard that is quite different from that of the majority of Arabs. As regards poliomyelitis, the Jews, in fact, may be compared with the British and American troops coming into these areas. It is, therefore, of particular interest to note in the study quoted by Dr. Paul that poliomyelitis was not common among the large native Arab population and that the highest prevalence was among the Jews. It was stated that the average attack rate was 20 times higher among the Jews than among the Moslems. The point of this discussion is that, while cases of poliomyelitis may be relatively rare or uncommon among the poor native populations of the Middle East, the disease does occur in that area and the possibility exists that the infection may actually be very much more widely disseminated in the area than it is in the areas from which the U.S. and British troops came. Thus, the lesson of importance to military preventive medicine regarding poliomyelitis in the Middle East is that the native population, particularly that portion of it with the poorer hygienic living conditions and standards very
likely provided a considerably greater source of poliomyelitis virus than was ordinarily present in the United States or in Britain and that, accordingly, one might expect a higher rate of poliomyelitis among troops living in close proximity to the local population. The possibility that unusual immunologic types of virus may also have been responsible for the increased incidence of poliomyelitis among the British and U.S. Armed Forces must be considered but has not as yet been investigated. In this regard, it is noteworthy that at least two of the strains of poliomyelitis virus (MEF1 and Phillips) recovered from fatal military cases proved to be of the Lansing type, which is very widely disseminated throughout the world.
Philippine Islands, 1944-45
The first case of poliomyelitis in U.S. forces had its onset 16 days after the beginning of the occupation of Leyte on 20 October 1944. This was followed by a relatively high incidence of the disease which was particularly intriguing because it represented the first appearance of poliomyelitis among U.S. forces in SWPA (Southwest Pacific Area).15 According to the statistical health reports, 39 cases of poliomyelitis occurred during the months of November and December 1944 in a force which varied from an initial strength of about 200,000 to a little over 300,000 at the end of the year, and 246 cases for all of 1945 for a force which varied from 300,000 to 600,000. There is reason to believe, however, that this does not include all the cases. For example, the report of the virus team of the 19th Medical General Laboratory16 lists 37 paralytic cases with 12 fatalities and 10 nonparalytic cases among Army, Navy, and Marine Corps personnel, with onset in November and December 1944, which they studied at only two hospitals on Leyte, while the statistical reports at the Office of the Surgeon General list only 39 cases with 14 fatalities. Furthermore, in 1945, the illness of patients with paralysis reaching the larger hospitals after some delay was frequently diagnosed as Guillain-Barré syndrome (infectious polyneuritis), because the cerebrospinal fluid at the time of examination exhibited an increased protein content without pleocytosis.17 Since this "albuminocytologic" dissociation is very common in poliomyelitis after the acute stage, it is not improbable that many of the Guillain-Barré cases were convalescent poliomyelitis.
With few exceptions, the data presented reflect almost entirely the incidence of paralytic poliomyelitis. Thousands of cases of fever of unknown origin which were generally regarded as atypical dengue occurred on Leyte18 and
elsewhere in the Philippine Islands, frequently in close association with cases of paralytic poliomyelitis. Large numbers of iced serums collected by Maj. (later Lt. Col.) Frederick T. Billings, Jr., MC, from such cases of "atypical dengue" in Leyte and others collected subsequently by Lt. Col. (later Col.) Cornelius B. Philip, SnC, were tested by the author in many human volunteers in the United States without the recovery of dengue virus, although a similar procedure resulted in the recovery of many strains of dengue virus from atypical cases in New Guinea. It is not improbable that many of these cases of so-called atypical dengue were actually abortive poliomyelitis, although actual proof is lacking.
An incidence of 246 predominantly paralytic cases of poliomyelitis with 52 deaths for a population of 300,000 to 600,000 (the data for U.S. forces in the Philippines in 1945) would constitute a sizable epidemic in any American city, except that in an American city approximately 85 percent of those cases would have occurred in children 15 years of age or younger. To account for this relatively high attack rate in individuals of Army age, one is forced to assume that the dose of virus to which these men in the Philippines were exposed was exceptionally great, that the immunologic types of virus were unusual for them, or that both of these conditions existed. While the total number of men affected is still very small to be significant from the point of view of military operations, serious problems were, nevertheless, raised for the medical installations, particularly since cases of ascending paralysis with involvement of the respiratory muscles were very numerous.
The distribution of cases during different months of the year (table 43) indicates that the virus was available the year round, although the attack rates frequently varied during different months. A good deal of light was thrown on the epidemiological pattern by two studies carried out by officers of the 19th Medical General Laboratory on the first group of cases which occurred in Leyte in 1944 and on an outbreak at the Laoag Army Air Base in 1945.
Outbreak on Leyte, 1944.-The first case of poliomyelitis had its onset on 5 November 1944, 16 days after landing, in the first group of troops to reach the island. Thirty-seven paralytic cases and ten nonparalytic cases were then seen at one evacuation hospital and one station hospital. The following observations from the epidemiological notes of the virus team are of special interest:
The cases of clinically evident anterior poliomyelitis have occurred in widely scattered areas at a distance from fifty yards to thirty-five miles from the point of hospitalization. In one instance three cases occurred in the same U.S.M.C. organization but in different units. With rare exceptions there is no history of contact between the units involved. With one exception, no two men came to Leyte on the same ship. The men have come from the United States, the Hawaiian Islands, Australia and many points in and around New Guinea.
In only one instance [a medical corps soldier] has clinically evident paralysis occurred in a man who was in known contact with poliomyelitis patients. This man took care of respiratory cases the first week in December and developed his illness
within 14 days. He was also a member of the 124th Station Hospital detachment in which several possible abortive or preparalytic cases have occurred.
There was no uniform history of an increase in upper respiratory infections in the units involved. Seven among 23 of the patients report having had diarrhea or dysentery since arriving on Leyte and some of these episodes occurred within the possible incubation period of the poliomyelitis. This has no statistical significance in view of the prevalence of diarrhea and dysentery occurring under combat conditions. It does indicate, however, that many of the patients had ingested human feces since arriving on the island, some of which possibly could have contained poliomyelitis virus.
In the presence of frank paralytic poliomyelitis, increased interest has been attached to men with headache, fever, stiff neck and orbital pain. * * * Several of these men [observed in the two hospitals where the virus team worked] have had an increased spinal fluid cell count, predominantly lymphocytic in character, but have made a rapid and uneventful clinical recovery with no evidence of paresis or paralysis. Such men may constitute the abortive and preparalytic cases which are to be expected in the usual outbreak of poliomyelitis. Early in November 1944, four men with similar findings were diagnosed as benign lymphocytic choriomeningitis in the 165th Station Hospital. * * * Several such questionable cases were definite contacts of known poliomyelitis patients or occurred simultaneously within a group. Six men in the 893d Clearing Company operating the civilian hospital at Palo simultaneously developed fever and severe headaches. Only one developed paralysis. During this time the personnel of the 91st Station Hospital were working with the 893d Clearing Company prior to assuming complete charge of the civilian hospital and at least three of their men developed similar symptoms within 2 weeks. The entire picture is complicated by the fact that dengue fever is apparently occurring here and presents prodromal symptoms initially comparable. [The "dengue" observed in "thousands" of soldiers in Leyte was atypical without rash.
and tests in many human volunteers in the United States of serum specimens, which had been obtained in Leyte within 24 hours after onset, yielded no virus.19]
No evidence of poliomyelitis has appeared among the Filipinos although several hundred passed through the civilian hospital during the time the men mentioned above were ill; in addition many civilians are employed in the hospitals. In the Philippine Islands poliomyelitis is considered to be a disease of white people. The last definite case of poliomyelitis reported from Leyte occurred in 1938. Civilian health records in the area where many of the soldier cases of poliomyelitis have occurred are remarkably complete because the Japanese authorities required a daily health report on infectious diseases occurring among the civilians. Local Filipinos have now been exposed to poliomyelitis for more than six weeks. To date no cases of paralysis have been reported to this investigator. The estimated population of Tacloban in December 1943 was 33,795 and of Palo, for the same period, 27,335.
The characteristic clinical manifestations in the paralytic cases and the histological findings in the brain and spinal cord of a number of the fatal cases left little doubt regarding the diagnosis. However, there was considerable speculation as to whether the virus was brought in by the troops who came from the United States or whether it was of local origin. Col. Henry M. Thomas, Jr., MC, the medical consultant who studied these patients on Leyte, stated: "* * * certain facts seem fairly sure, however, and these point to the introduction of the reservoir into Leyte with the troops."20 The facts responsible for this impression were, first, that no recent cases of poliomyelitis had been uncovered among Filipinos and, second, that in one area a case had developed 5 days after the soldier had arrived in Leyte. The fact that no recent cases of poliomyelitis had been uncovered among the Filipinos cannot be taken to indicate that poliomyelitis virus was not in fact being disseminated rather abundantly by the native population. Antibody studies in various parts of the world among populations with a negligible incidence of paralytic poliomyelitis living under primitive or poor sanitary conditions have suggested that poliomyelitis virus is widely disseminated among them. The second fact regarding the development of a case of poliomyelitis within 5 days after arrival in Leyte has no bearing on the reservoir of the virus since the onset was well within the incubation period of the disease. Furthermore, this particular patient had arrived in Leyte on 13 November at a time when the first cases of poliomeylitis had already made their appearance in other units which had arrived earlier. The following observations strongly favor Leyte as the reservoir of the virus:
1. The invasion force spent, on the average, more than a month on board ship without the appearance of any cases of poliomyelitis.
2. The first case did not appear until 16 days after the invasion began.
3. The cases were scattered widely as regards time and space among many different units which had no contact with one another.
4. No poliomyelitis was observed in these troops while they were in New Guinea and other islands in the Southwest Pacific, where they were stationed beyond the range and influence of native villages.
5. The incidence of poliomyelitis continued to be high among the American forces in the Philippines in 1945 and 1946 with attack rates markedly in excess of those encountered in the Army in the United States.
An examination of the dates of onset of the cases in two different regions of Leyte suggests that the reservoir was continuous rather than temporary and explosive as was the case, with one exception, in the outbreaks in military units in the United States. Furthermore, the strikingly different case fatality rates in the two areas (62.5 percent in the Palo-Tacloban-Carigara area of north Leyte and 5.3 percent in the Dulag areas of central Leyte) strongly suggest that strains of virus of different virulence may have been prevalent in the two areas. Although Colonel Thomas was inclined to correlate this difference in mortality with the fact that one force was staged in New Guinea where mortality from the disease was high, and the other force in Hawaii, an examination of the individual records of the patients from the Dulag area shows that some of the patients came from the New Guinea area and some from Hawaii. Similar differences in mortality rates have also been encountered in different outbreaks in military units in the United States as well as during different epidemics at different times among civilian populations.
If one grants that the reservoir of virus was indeed in Leyte and other parts of the Philippine Islands, it is of interest to note the conditions which could easily have contributed to its dissemination among U.S. military personnel. Since it has been abundantly demonstrated that the feces of patients and of inapparently infected individuals constitute a rich source of virus, and since experimental infection by the oral route has been proved to reproduce the inapparent, nonparalytic and paralytic manifestations of poliomyelitis, one cannot disregard the various routes by which human feces, potentially infected with the virus, may reach susceptible individuals. The following description of the conditions, in the Philippines, in part I of the 1945 Annual Report of the Chief Surgeon, USAF WESPAC (U.S. Army Forces, Western Pacific), clearly indicates the potential source of poliomyelitis virus as well as of other infectious agents predominantly present in human feces:
With the invasion of the Philippines certain new disease problems were encountered and the question of sanitation assumed new importance because of the civilian population. * * * Sanitary habits of the civilian population * * * menaced the health of the troops. The situation was more acute than it might otherwise have been because no restrictions were placed upon fraternization with the civilian population. Troops ate large quantities of food and delicacies prepared by friendly Filipinos under uncertain sanitary conditions, a fact which goes far to explain the high incidence of diarrhea and dysentery encountered in the Philippine operations. * * * Satisfactory sanitation was at
all times difficult to achieve, not only because of the civilian population and the tendency to station troops in or near barrios and towns, but also because many areas had high water tables which were further heightened by torrential rains.
Due to the lack of latrines, the heavy fly population, and the civilian habits of defecating on the ground, it was not surprising that the troops stationed in the midst of densely populated regions exhibited a high incidence of those bacterial, protozoal, and viral infections which are predominantly found in human feces. Amebic dysentery, seldom seen in New Guinea, was encountered in high rates on Leyte, even though surveys of the civilian population of Leyte disclosed pathogenic amebae in less than 1 percent. The aforementioned annual report for 1945 also contained the following statement: "Combat troops of the Sixth Army suffered much more from infectious hepatitis than did service troops in the first quarter of 1945. The rate for Sixth Army troops on Luzon was 50 per 1,000 per annum in February and reached about 200 per 1,000 per annum in May."
It is of interest, in this respect, that one of the Leyte patients who developed paralytic poliomyelitis on 6 December 1944 also came down with infectious hepatitis 11 days later.
Outbreak at Laoag Army Air Base, 1945.-This outbreak, which was investigated by Lt. Col. A. J. French, MC,21 of the 19th Medical General Laboratory, is interesting not only because of its explosive character and focal concentration but also because it points to potential sources of virus in a military installation which is located at some distance from an inhabited area. Although the strength is not reported, 22 cases occurred in this outbreak. The majority of the cases occurred during the month of May, and the onset of at least 8 paralytic cases occurred between 19 and 22 May. Because 7 patients had been evacuated by the time Colonel French arrived, his study was limited to 15 patients, among whom only 4 were nonparalytic. Three of the total of twenty-two died, and a complete histologic examination of the nervous system in one case confirmed the diagnosis. The following epidemiological observations were made :
1. The units in the main bivouac area had occupied areas previously utilized by Japanese troops. Open latrines with myriads of fly breeding areas were scattered throughout the troop areas.
2. Screening and DDT were not generally available.
3. While natives were not housed near the troop areas, there must have been some within one-half mile of the reservation, since on 1 June 1945, the military governor issued a directive regarding the construction and fly-proofing of latrines by Filipinos living on the Air Base Reservation or within one-half mile; furthermore, Filipino laborers working at the base had their own latrines there.
4. Twenty of the 22 cases were housed in an area covering approximately 1,000 square yards.
5. Bathing in the Laoag River was not a common occurrence due to the fact that it was some distance from the main troop area. Five of the cases had bathed in the river
6. An interview with Dr. Valdez, Director of the Ilocos Norte Provincial Hospital revealed the possible occurrence of seven cases of paralysis in Filipino infants which was attributed by Dr. Valdez to poliomyelitis. He stated that these cases occurred in May and June of 1945.
Colonel French's final conclusion is also worth quoting:
Increased attention to sanitation is mandatory, particularly early in the course of establishment of an Army Base. Flies, mosquitoes and rodents must be controlled. Native dwellings must be kept at a distance from Army installations and latrine facilities must be made available to native laborers at Army Bases. Screen and DDT must be utilized on latrines, kitchens and mess halls.
The statistical health reports list a total of 112 cases of poliomyelitis among American forces for the period 1942 to 1945 with a mean annual attack rate of 0.26 per 1,000, which, however, varied by year from 0.22 to 0.53. For China in 1945, 28 cases are listed, yielding a rate of 0.65 per 1,000 per annum. Col. Herrman L. Blumgart, MC, and Maj. George M. Pike, MC,22 writing about poliomyelitis in the India-Burma Theater, indicated that cases occurred sporadically during all months of the year with a case fatality rate of 20 to 25 percent. These authors observed:
The incidence of respiratory and/or bulbar involvement in the American military personnel was apparently high * * * The principal problem was the supply and maintenance of the respirators. With sporadic cases occurring at installations thousands of miles apart and often in relatively secluded places, it was imperative to maintain respirators at certain key points in useable condition ready for immediate air transport.
While there are no specific reports on the circumstances under which poliomyelitis occurred among U.S. troops in this theater, it is not unlikely that they were similar to those described in the Philippines. In August 1946, the author had an opportunity to study an explosive outbreak of poliomyelitis (5 paralytic cases with 4 deaths and 25 nonparalytic illnesses) among a battalion of U.S. Marines stationed in the midst of the native population in Tientsin, China. The author was impressed with the abundance of feces on the banks of a recently dredged canal in the vicinity of the barracks and of the ample opportunities which flies had for contaminating the food consumed by the Americans. Brigadier McAlpine strongly stressed the importance of poor sanitation and fecal contamination of food as a factor in the epidemiology of poliomyelitis in British troops in India. He related the strikingly higher incidence among British officers as compared with that in other ranks to the fact that officers' messes are generally catered to by contractors and serviced by native help under poor sanitary conditions. He described an instance of an explosive, apparently foodborne outbreak among officers who stayed for a short time at a private hotel in south India.
Poliomyelitis research during the period 1940-45 was carried on by several members of the Commission on Neurotropic Virus Diseases of the Board of Investigation and Control of Influenza and Other Epidemic Diseases in the Army, although not specifically under Army auspices. The work was concerned predominantly with the systems affected by the virus in human beings, the pathways of excretion, the extrahuman sources of virus in nature, the occurrence of virus in sewage and filth flies, the nature of the experimental disease produced by oral infection, the contamination of food by flies under natural conditions in epidemic areas, and the demonstration that combating flies with DDT from the ground and air after an urban epidemic is well established has little or no effect on the subsequent course of the outbreak. Several strains of virus, including two of the Lansing type, were recovered from military personnel in the Middle East and the Philippines. Material collected in 1945 from military personnel in the Philippines and sent to the New Haven Laboratory of the Neurotropic Virus Commission yielded 10 strains of poliomyelitis virus-5 from the feces of patients with acute cases and 5 from the central nervous systems of individuals with fatal cases.23 When the methods for definitive immunologic classification of different types of poliomyelitis virus have been worked out, the availability of these strains will permit their comparison with others prevalent in the United States. The laborious methods required for the detection of poliomyelitis virus have precluded any extensive virological investigations of outbreaks in military installations, but the observations on the epidemiological patterns of the disease among the Armed Forces at home and abroad proved to be illuminating.
SUMMARY AND EVALUATION
The total number of cases of poliomyelitis which occurred in the U.S. Army during the period 1942-45 can only be approximated. On the basis of the analysis of individual medical records, which is regarded as the source of the ultimate official statistics, the number of cases in the entire Army for the 4-year period was 1,006, with 267 deaths, representing a case fatality ratio of 26.5 percent. It should be pointed out, however, that the statistical health reports, which contain the preliminary and not necessarily the final diagnosis and which have been the source of previously published statistics on poliomyelitis in the Army, list 1,326 cases for the 4-year period from 1942 to 1945. According to the statistics based on the individual medical records, the attack rate per 1,000 troops per year among those stationed in the United States varied from 0.02 to 0.04 and averaged 0.03. This morbidity rate is of the same order of magnitude as that for civilians of similar age in the United
States and indicates that the conditions peculiar to Army life in the United States do not involve a greater risk of contracting poliomyelitis.
As a rule, poliomyelitis occurred in the form of isolated cases which were not followed by outbreaks in the units in which they appeared. Only two small outbreaks occurred in Army personnel in the United States, and both were of the explosive, localized type suggesting primary infection from a common source over a limited period of time. Several additional outbreaks which occurred in Navy personnel in the United States were also of the explosive type, occurring under circumstances which strongly suggested that infection was conveyed by some article of food contaminated by a carrier or flies. These outbreaks were self-limited without tendency to spread by contact in other units to which individuals from the epidemic focus may have moved during the incubation period of their disease. Only one outbreak in the United States was characterized by the appearance of groups of cases in waves over a period of 3 months, and this occurred in a California college in which Navy students were in training. However, interestingly enough, no secondary cases could be traced to contacts of the students outside the college. These isolated outbreaks in the United States in which attack rates were as high as 2.5 percent indicated that under special circumstances, perhaps in instances of a particular strain or immunologic type of virus, young adults of military age can be highly susceptible to poliomyelitis. The fact that the mortality in these individual, isolated outbreaks varied from none to 36 percent would suggest that different strains of poliomyelitis virus might also vary considerably in virulence.
Among U.S. troops in the European theater the incidence of poliomyelitis was somewhat lower than among troops stationed in the United States, except for a brief period in 1942, and no outbreaks were recorded. It is also of interest that the special conditions of crowding on troopships were not conducive to the spread of poliomyelitis virus, even when two individuals with cases embarked during the incubation period and developed the disease en route.
The incidence of poliomyelitis among U.S. troops in the Middle East, the Philippines, and China-Burma-India theaters was several times as great as that in the continental United States. The increased incidence was not due to isolated explosive outbreaks, although a few of those occurred, but rather to what appeared as an almost continuously available rich source of the virus. The same unsanitary conditions and proximity to native populations which gave rise to high attack rates of bacillary dysentery, amebic dysentery, and infectious hepatitis also were epidemiologically associated with the increased incidence of poliomyelitis. Poliomyelitis did not occur among troops in the Southwest Pacific Area in New Guinea and in other primitive tropical or subtropical regions where the military installations were beyond the range and influence of native villages. However, within a very short time after
these same troops moved to the Philippines into the midst of congested, native villages and towns with sanitation of the worst possible order, poliomyelitis appeared in unexpectedly high numbers along with the other infections whose etiological agents are known to occur predominantly in human feces. Although the actual number of cases of paralytic poliomyelitis was small by comparison with the incidence of the other infections in this category, it presented many emergency problems in medical management because of the frequent involvement of the muscles of respiration.