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THE PUZZLER IN POLIO EPIDEMICS
In an article in the June 28, 1947 issue of the Journal of the American Medical Association, Dr. A. B. Sabin, a leading investigator in polio, discusses certain problems which have baffled students of the disease. I shall state some of the problems he mentions and shall attempt to throw some light on their solution.
1. Dr. Sabin states: "No circumstance in the history of poliomyelitis is so baffling as its change during the past 50 years from a sporadic to an epidemic disease."
An increasing consumption of sugar, as shown in the following table, helps explain this change in the incidence of the disease.
TABLE NO. 2
THE CONSUMPTION OF SUGAR IN THE UNITED STATES
Years
Yearly Average Pounds per Capita
1880-1890
44
1890-1900
56
1900-1910
65
1910-1920
82
1920-1930
100
1930-1937
95
1939
103.2
2. Dr. Sabin writes: "Another peculiar circumstance which may contain an important clue is that epidemics have occurred with greatest frequency and severity in the very countries in which sanitation and hygiene have undoubtedly made the greatest advances."
I offer the following explanation: Advanced sanitation and hygiene are, as a rule, to be found in the wealthier countries. Advanced sanitation and hygiene have helped prevent such diseases as typhoid fever, cholera, malaria, and tuberculosis, because the environment has been controlled by purification of water and milk, by drainage of swamps, by proper sewage disposal, and the organisms responsible for these diseases have been "kept away from our doors." The fact that polio has not been prevented by advanced sanitation and hygiene indicates that its incidence is controlled and influenced by factors quite different from the factors that bring about the spread of typhoid and the other diseases. As previously stated, advanced sanitation and hygiene are to be found in the richer countries, and one of the unfortunate evils that accompany wealth is the consumption of sugar in the form of luxury foods such as ice cream, candies, soft drinks, cakes, pies, pastries, and the like. Poor countries cannot afford luxury foods, sanitation and hygiene. That is how I would explain the greater incidence of polio in countries with advanced sanitation and hygiene. The following table shows the extreme differences in sugar consumption in various parts of the world and it will be readily noted that the countries with the lowest sugar consumption are most backward in sanitation and hygiene.
Thus we see that sugar consumption is by far the greatest in the richer countries where one would also expect to find advanced sanitation and hygiene. Epidemics have occurred with the greatest frequency and severity in the high sugar consuming countries. In fact, epidemics have never been reported in the natives of the low sugar consuming countries, such as China.
3. Dr. Sabin states: "In my opinion, one of the most important problems in the epidemiology of poliomyeitis* is the determination of factors relative to virus, host, and environment, which are different in cities like New York, Chicago, Minneapolis, Los Angeles, and Denver, and many others in the United States with histories of large outbreaks of the disease, and cities like Peiping, Tientsin and Shanghai, occupying the same latitude in China in which only rare sporadic cases have been reported thus far, despite the presence in these cities of western-trained physicians who could not have missed such outbreaks in the native population if they had occurred."
* The sum of what is known about polio epidemics.
TABLE NO. 3
SUGAR CONSUMPTION BY GEOGRAPHICAL DIVISIONS
(Crop Year Sept. 1, 1938, to Aug. 31, 1939)
Per Capita Consumption
Country (Pounds — Raw Value
United States 103.2
Canada
102.9
Mexico
37.1
Other North America 41.2
Argentina
71.0
Brazil
51.7
Other South America 28.8
Sweden
119.3
United Kingdom 112.6
Switzerland
85.1
Holland
89.4
Germany
63.3
Italy
21.3
Poland
29.8
Rumania
14.6
Spain
17.2
China
3.2
India
24.3
Japanese Empire 29.1
Java (Dutch East Indies) 11.6
Other Asia
13.0
Algeria, Morocco, and Tunisia 44.4
British South African Union 58.6
Egypt
20.4
Other Africa
37
Australia
114.5
Other Oceania 81.0
In line with the explanation offered to problem 2, I would state that here again the extreme differences in per capita sugar consumption between China (3.2 lbs.) and the United States (103.2 lbs.) afford a ready explanation for the occurrence of epidemics in the cities of the United States and the absence of epidemics in the cities of China.
4. Dr. Sabin tells how polio occurred among American troops in China, Japan, and in the Philippines, in spite of the fact that there were no outbreaks of polio at the time among the native children and adults in those areas in which the troops were located. A report on polio in the Philippines in 1936 stated that 16 of 17 patients with the disease in Manila were Americans. In 1945 there were 246 cases of polio with 52 deaths among American troops in the Philippines according to reports to the Office of the Surgeon General. A nd, since the end of combat in the Philippines, polio has been among the leading causes of death in American troops; but checks have revealed no outbreaks of polio among the surrounding native population. In fact, epidemics of polio have never been observed among the natives of the Philippines. Why has the disease been confined to the American troops in these countries?
Dr. Sabin also witnessed an outbreak of polio in the summer of 1946 among American marines stationed in the Tientsin area of North China. Four men died, one was severely paralyzed, and at least 25 others had nonparalytic attacks. There was no outbreak of polio among the natives at the time. Dr. Grice, a British physcician in Tientsin for 25 years, informed Dr. Sabin that while he not infrequently saw paralytic polio in children in the foreign colony he rarely saw the disease among the Chinese. The extraordinarily uncommon occurrence of polio among the yellow races living in North China was also reported by Zia in 1930.
I offer the following explanation for the occurrence of polio among American troops in China and the Philippines: The Americans took their dietary habits with them overseas. All during the war, as soon as local combat conditions permitted, ice cream, candies, soft drinks, cakes, and the like, became available to American troops. Ice cream manufacturing equipment followed soon after combat equipment. I saw American troops consume great quantities of candy bars when they lost their appetite for the monotonous K and C rations. It was felt that our men would feel at home, not get homesick, and have better morale if sweets were available. Thus, I submit, polio occurred among the Americans and not among the natives because the natives did not consume the amount of sugar the Americans did.
5. Dr. Sabin writes: "Intimate human contact….does not by itself explain the recurrent summer epidemics of paralysis….With the present high incidence of the disease among children of school age in the United States, it is remarkable that, unlike certain other infections of childhood, the epidemics of paralysis occur during the very months when the children are away from school."
I submit that this problem may be answered, in part, by stating that when children are away from school during the summer they have more time for physical activities which may at times be excessive and so they become predisposed to polio as previously discussed in the chapter on Physical Exertion and Polio. Also, during the summer they get hot and thirsty, consume more sweet cooling beverages and foods, and thereby run the risk of low blood sugar.
6. Dr. Sabin also states: "All this brings one back to another old question in the epidemiology of poliomyelitis, namely: do more people acquire the poliomyelitis virus during the summer and early autumn months, or is there only a difference in the ratio between the number exhibiting the paralytic and inapparent nonparalytic forms of the disease during the different times of the year? If there were only some way of answering this question by direct laboratory tests instead of by speculation, analogy or evaluation of probabilities, one could end the controversy between those who maintain that certain unknown changes in the host rather than increased dissemination of the virus, are responsible for epidemics and for the greater incidence of the disease……Why does paralytic poliomyeitis, with only rare exceptions remain practically dormant during more than two thirds of each year, appearing in only an occasional person, and then seems to explode during the late summer and early autumn?"
In line with the ideas heretofore expressed, I would say that polio is more prevalent during the summer because of a change in the host. This change is a chemical one, namely, an increased incidence of low blood sugar brought on by an increased consumption of sugar in the form of cooling foods and beverages and, perhaps, a reduction in protein foods. Excessive physical exertion incidental to summer outings and vacations may further predispose to low blood sugar.
Dr. Sabin makes the following significant remarks regarding quarantine measures during polio epidemics: "Polio virus is present for a short time in the throat and more frequently and for a longer time in the intestinal tract and stools of certain apparently healthy people as well as of acutely paralyzed patients during an epidemic…..There is no evidence that the virus is ordinarily present in the nose or that droplets emitted from the respiratory tract play a significant role, if any, in the dissemination of the virus……Measures designed to minimize spread by droplet infection such as closing of movies and churches …are not warranted."