Poliomyelitis Distribution in the United States

By ROBERT E. SERFLING, Ph.D., and IDA L. SHERMAN, M.S.

IN THE EARLY summer of 1894 inhliabitantsof the Otter Creek Valley in western Ver-

mont became aware of a strange paralyticdisease in their community. It seemed to se-lect younger children as particular victims al-though a few adults were also affected. Thisfirst notable epidemic of poliomyelitis in theUnited States was carefully investigated byDr. C. S. Caverly, president, Vermont StateBoard of Health. His field studies, consti-tuting a classic model of "shoe-leather" epi-demiology, mark the beginning of our modernknowledge of poliomyelitis. In the followingyears other investigations conducted in theCaverly pattern demonstrated the extensivedistribution of the disease and indicated theneed for systematic morbidity reporting.

Massachusetts, in 1907, was the first State( 1) to require notification of all cases of polio-myelitis. In 1910, the Surgeon General of thePublic Health Service requested all States tosubmit reports on poliomyelitis for 1909 and1910. This initiated national reporting ofpoliomyelitis, although regular inclusion of re-ports from all States was not achieved untilabout 1922. Since that time a large body ofdata has accumulated, forming an increasinglycomprehensive base for continuing analyses ofelementary epidemiological characteristics,such as secular trends, geographic distribution,and seasonal variation. A number of excellentanalyses have been published (2, 3? 4, 5), but

Dr. Serfling and Mrs. Sherman are chief and assistantchief, respectively, of the statistics section, epidemi-ology branch, Communicable Disease Center, PublicHealth Service, Atlanta, Ga.

the nmost recent iniclude only the years through1946 in the United States (6, 7). Sabin (8) re-viewed epidemiological clharacteristics of anumber of poliomyelitis outbreaks throughoutthe world.

Certain epidemiolog,ical characteristics ofpoliomyelitis have changed with time. In theUnited States, annual rates both of reportedcases and of deaths have shown an upwardtrend, particularly during the past decade.In earlier decades a lower inicidence was ob-served in southern States than in northernStates. This difference is less apparent inrecent years.

Continuing studies and analysis of these ele-mentary epidemiological characteristics andtheir changes are indicated for any infectiousdisease that remains as a serious problem in thecountry. Furthermore, discovery of the valueof gamma globulin in the prophylaxis of polio-myelitis (9, 10) poses difficult problems as tothe best way to utilize available supplies.The fullest possible knowledge of the current

epidemiological pattern of poliomyelitis as re-vealed by morbidity and mortality reports maybe useful in guiding administrative decisions.For these reasons the present paper has beenprepared. The past history of poliomyelitisas recorded in published literature and officialreports was reviewed anid special attention wasgiven the period 1932 to 1952 with particularemphasis on changing patternis of the past 5 to10 years.

National Incidence

The trend of the nationial case and death ratesin the United States durinig the period 1910-52,is shown in figure 1. Since both cases ancd

Vol. 68, No. 5, May 1953 453

deaths were not reported from the same groupof States during earlier years, the rates in figure1 were based on reports from those States whichreported both cases and deaths. The record ofnational incidence of poliomyelitis in the UnitedStates falls naturally into four periods:

1. Prior to 1909, when information on inci-dence, except for a few States, depended on de-scriptive accounts in the epidemiological litera-ture.

2. From 1909-16, when published reportswere available from some States. These weresupplemented by special studies of Lavinder,Freeman, and Frost, and their summaries givemore complete information on the period.

3. From 1917 through the epidemic year 1931,during which time reporting gradually becamemore complete. By the middle 1920's mostStates were reportinig annually.

4. From 1932 until the present, during whichtime national reporting of both cases and deathshas been essentially complete. Because of theobvious differences which characterize nationalreporting in the different periods, they are pre-sented separately in this discussion.

Early Year8During the 1894 outbreak in Vermont, Cav-

erly collected information on 132 cases. Ofthese, 119 had shown paralysis, 7 had died be-fore paralysis was noted, and 6, although ex-hibiting symptoms characteristic of early stagesof the illness, had not developed paralysis. InRutland, the largest community in the affectedarea, 55 of the 12,000 inhabitants had beenstricken-an attack rate of 460 cases per 100,000population. In nearby Proctor, a town of 2,000persons, 27 cases had occurred. The remaining50 cases were scattered through a dozen smallcommunities in the area.Two years later, in a final report of his in-

vestigations (11), Caverly concluded that thedisease was "epidemic poliomyelitis," possiblya variant form of the "infantile paralysis"which in the United States had been knownprincipally as an endemic disease of relativelyinfrequent occurrence.In the succeeding years similar outbreaks oc-

curred with increasing frequency in many partsof the country. In 1908 two papers (12, 13)

summarized accounts of 17 poliomyelitis epi-demics in the United States and others through-out the world. By this time, outbreaks hadbeen described in Alabama, California, Florida,Illinois, Maine, Massachusetts, Michigan, Mis-souri, New York, Pennsylvania, and Wisconsin.These seem generally to have been of smallerscale than the Rutland episode.In New York City, however, the 1907 out-

break was the largest then recorded in anyplace. The impact led to an extensive retro-spective investigation initiated in October of1907. The study (14) was conducted by mailand produced detailed information on 752 cases.It was estimated that in all, about 2,500 caseshad occurred. Although cases were somewhatconcentrated on the east side of Manhattan, theepidemic had extended northward to Pough-keepsie and throughout the western end of LongIsland. The case fatality was estimated to be5-7 percent, about half that of the Rutlandoutbreak.In Massachusetts, where smaller outbreaks

had been noticed since 1893, incidence was alsohigh in 1907 and the State made poliomyelitisa reportable disease. In 1908, 136 cases werereported in Massachusetts (1). In midwesternMinnesota, 150 cases were recorded, and in Wis-consin, 408. In the following year, 1909, agreat outbreak struck in Nebraska. Descrip-tion of this epidemic (15) was also based on aretrospective study. In answers to letters, 58physicians reported 999 cases in 18 counties.Thle greatest number of cases, 384, was reportedfrom Polk County, with a population of 10,000.Douglas County (1910 population, 168,546) re-ported 79 cases, a rate slightly less than 50 per100,000 population, and comparable to that ofthe New York City epidemic of 1907. In 1910Massachusetts reported 845 cases, Pennsylvania1,112, and in the midwest, Minnesota and Iowaeach recorded more than 600 cases. In the farwvest, nearly 400 cases occurred in the State ofWashington. On August 9 of that year (1910)the Surgeon General of the Public Health Serv-ice initiated the request that started nationalreporting of poliomyelitis. In the same yearprovision was also made for separate classifi-cation of poliomyelitis deaths in the nationalvital statistics summary.

Public Health Reports454

Figure 1. Annual poliomyelitis case and death rates in States reporting both cases and deaths,United States, 1910-52.

2

-

ac

CcC

0w

0wa.4

z0

!a4

n

-a00~00.00

w0..bJ!acr

;2'J

A. ARITHMETICAL RATE SCALE

j40

;30L 4 | |CASE RATE

20

ioDEATH RATE

1910 1915 1920 1925 1930 1935 1940 1945 1950YEARS

40

B. LOGARITHMIC RATE SCALE

206CASE RATE

108~~~~~~~~~~~~~

6

4'

DEATH RATE

.6 iI V

..........2

1910 1915 1920 1925 1930 1935 1940 1945 1950YEARS

SoIBEc: Cases, 1910-50-Public Health Service: The Notifiable Diseases (Pub. Health Rep. Supp.).1951-National Office of Vital Statistics: Reported Incidence of Notifiable Diseases in the United States, 1951,Annual Supplement to Weekly Morbidity Report, vol. 2, No. 53, 1953. 1952-National Office of Vital Statistics:Morbidity and Mortality Weekly Report, vol. 1, Nos. 1-53 inclusive. Deaths, 1910-49, Vital Statistics of the UnitedStates. U. S. Bureau of the Census, 1910-44; U. S. Public Health Service 1945-49. 1950-51 data from advancereleases, 1952 data from 10 percent mortality sample, Jan.-Nov., National Office of Vital Statistics.

* I

Vol. 68, No. 5, May 1953 455

Years 1909-16

For 1909 only 3 States submitted morbidityreports to the Public Health Service and in thefollowinig 7 years the numbers ranged from 11to 29. After the 1916 epidemic, Lavinder, Free-inan, and Frost published a summary of mor-bidity and mortality for the period 1909-16which incorporated data from a number ofStates not included in the earlier national sum-maries. For the years 1909-15, they obtainedadditional State morbidity reports and alsomortality reports for some States in which nomorbidity data were available. For the latter,estimates of cases were made from reportedpoliomyelitis deaths, assuminig a case fatalityrate of 20 percent. For States in which onlycertain cities were in the registration area,deaths for the entire State were estimated fromthose in the registration areas. Since Lavinder,Freeman, and Frost had noted that in Statesfor which registration was complete, the urbandeath rate was lower than the rural rate andthat a case fatality as high' as 20 percent oc-curred only rarely, they believed that error intheir estimates had been in the direction ofunderestimation. Because of the care whichwent into this study, their figures for annualincidence of poliomyelitis in the Nation for1909-16 are quoted below:

Cases per 100,000Year population1909__-- ___________-- _________------ 6.91910---------------------------------- 13.31911---------------------------------- 9. 51912---------------------------------- 8.51913- - ____________________________ 6.61914-5 _________-- ___-- ____--__--_-a.11915- - ___________________________ 5.11916 -_------------------------------ 28.5

During the a years following the 1910 out-breaks, the estimated national rates declined.In these years the largest outbreaks took placein 1912, wlhen New York reported 1,108 casesanid California, 531. These were the only in-stances in which a State reported more than 500cases, although Massachusetts, New York,Pennsylvania, and Virginia reported from 100to 500 cases annually, and Illinois and Ohio re-ported from 100 to 500 cases in 4 of the 5 years.The great epidemic of 1916, although leading,

to highlest rates in the northeastern States, also

Table 1. States reporting 20 or more polio-myelitis cases per 100,000 population in1916

Num-Eastern States ber of

cases_- __-

New Jersey -

New YorkConnecticut -

MassachusettsRhode IslandDelaware dPennsylvaniaMarylandMaine -

4, 05513, 223

9511, 92622279

2, 181352149

Caserate

13812976523637262619

Central andwesternStates

MinnesotaMichigan- -

Montana ---

Wisconsin

I~~~~~~~~~~~~~~~~

Num- Casecases rt

909 40616 2094 20

475 19

SOURCE: Lavinder, Freeman, and Frost (1).

struck severely in the north central area andin Montana. States with rates of approxi-mately 20 per 100,000 population or larger arelisted in table 1.For the year 1916, Lavinder, Freeman, and

Frost obtained morbidity reports from all butfour States, amounting to a total of 29,061 cases.From these they estimated the national rate tolhave been 28.5 cases per 100,000 population.

Table 2. Annual poliomyelitis case and deathrates, United States,' 1917-31

Year

19171918191919201921192219231924 -

1925- -

19261927-1928192919301931

Cases per100,000

populatioIn

4.82.92. 22. 46.12. 02.94.165.22.28. 8

4. 22. 3

7.512. 8

Deaths perNumber 100,000of States populationreporting death-reg-

cases istrationStates

373840424748494848484849494948

1.41.2.9.91.8.8.9

1. 11. 5.8

1. 81. 2

. 71. 21. 8

I Includes District of Columbia as a separate report-ing unit. States reporting cases not necessarily thesame as those reporting deaths.

SOURCES: Cases, Notifiable Diseases, Annual Reports,Public Health Service; Deaths, Death-RegistrationStates, Annual Reports, Vital Statistics of the UnitedStates.

Public Health Reports4565

The total number of cases in the District ofColumbia and the 27 States which reported tothe Public Health Service was 27,363. Amongthese States, the average rate was 41 cases per100,000 population.

Year8 1917-31After 1916, no additional efforts were made to

obtain complete information on reported casesof poliomyelitis. Annual case rates for the Na-tion, computed on the basis of the populationsof those States submitting reports, and deathrates for the death-registration States are shownin table 2. The period seems to have been oneof generally low incidence of poliomyelitis.National rates varied from 2.0 in 1922 to 8.8 in1927, except for the epidemic year of 1931, whenthe rate reached 12.8. Despite the generally lownational rates, outbreaks of moderate size werereported by a number of States.In 1917, the rate in Vermont was three times

the 1916 rate. In the early and middle 1920's,the north central and western States of Minne-sota, North Dakota, Montana, and Washingtonreported the highest rates in the country. In1927 and 1928 a dozen States, ranging fromMaine to California, reported from 21 to 49cases per 100,000 population. The 1931 out-break was largely concentrated in the New Eng-land and Middle Atlantic States, and in Mich-igan in the midwest. The highest rates oc-curred in Connecticut (69.6) and in New York(48.2).

Years 1932,5?Annual rates for the United States during

the period 1932-52 are shown in table 3. Afterthe 1931 outbreak, the annual national rates didnot exceed 10 cases per 100,000 population until1944. In 1943 the case rate was 9.3, the highestsince 1931, and in the succeeding years rose tosuccessively higher levels, until in 1952 both thecase rate (36.9) and the estimated death rate(2.0) were higher than in any year since the1916 epidemic. With the marked upward trendin the morbidity rate, there has been a slight butdefinite increase in the mortality rate. Thishas resulted in a progressive decline in the ratioof reported deaths to cases from 14.0 percentin the period 1932-36 to 5.8 percent in theperiod 1947-51.

Vol. 68, No. 5, May 1953247814-53--2

Table 3. Poliomyelitis case rates, death rates,and their ratios, United States, 1932-52'

Rates per Ra100,000 d4

population ratYear ____ __ c

!rCases Deaths

Cc

1932.-- 3.0 0.71933.--- 4. 0 .61934-- 5.9 71935- &85 .81936-- 3.5 .6

1937-. 7. 4 1. 11938_.. 1.3 .41939--- 5. 6 .61940-- 7. 4 .81941- 6.8 .6

1942- 3. 0 .41943-- 9. 3 .91944-. 14. 3 1. 01945-- 10. 3 .91946- 18. 4 1. 3

1947- 7. 5 . 41948-- 19. 1 1. 31949 28. 4 1. 81950 22. 0 1. 31951- 18. 6 . 9

19652- 36. 9 2 2. 0

tio ofeathte toase-ateper-ent)

23. 315.0o11.99.4

17. 1

14. 930. 810. 710. 88. 8

13. 39. 77.08. 77. 1

5. 36. 86. 35. 94. 8

5. 4

Aver-agecaserate

5.0o

5. 7

11.1

19. 1

5-yeardeathrate

0. 7

. 7

. 9

1. 1

Ratio ofdeathrate tocaserate(per-cent)

14. 0

12. 3

8. 1

5. 8

1 Case and death rates based on population of Statesreporting both cases and deaths.

2 1952 death rate estimated from 10-percent nationalsample of the National Office of Vital Statistics, Janu-ary through November 1952.

The morbidity rate for 1952 falls between thetwo estimates (see above) for 1916, while theestimated mortality rate for 1952 is only one-fifth as great as the 1916 death rate of 10.5 per100,000. The question of whether or not the1952 epidemic was more severe than that of1916 is obscured by several factors relating tothe population bases used in determining therates. In 1952 reports of cases and deaths wereavailable from all States, whereas for 1916 twoestimates of the morbidity rate are available,but neither of the populations oni which theseare based is the same as that of the 26 death-registration States for which the mortality ratewas 10.5 per 100,000. Also, the 1916 populationof the death-registration States coincidedclosely with the populations severely affected bvthe epidemic, while the 1952 estimated deathrate of 2.0 per 100,000 includes populations notin epidemic areas. In addition to these factors,

457

Figure 2. Poliomyelitis morbidity-average 5-year rates, major geographic divisions of the UnitedStates, 1932-36, 1937-41, 1942-46,,1947-51.

1932-1936 ^1937-1941 .k

LEGENDCases per 100,000 per annum

E. 0-4.9EJ 5.0-9.9

10.0-14.915.0-24.9

_ 25.0 AND OVER (MAXIMUM ATE,2S.5)

others must be considered: for example, im-provement in completeness and accuracy ofmorbidity reporting; and improvement in treat-ment, presumably resulting in lowered casefatality rates

Geographic Distribution

The geographic distribution of poliomyelitisin the United States during the last 20 years isdescribed for the nine major geographic divi-sions of the country from two approaches:average incidence in successive 5-year periodsand variation in annual incidence. Eachmethod gives emphasis to different aspects ofsecular changes in geographic distribution ofthe disease.

Average IntidenoeAycock (3), in studying distribution of polio-

myelitis in the United States during the period1910-27, and later Wells (4), in a study of theperiod 1915-29, came to the conclusion that in-cidence in the northern States had been dis-tinctly greater than that in the southern

portion of the country. Both of these studiesincluded the 1916 epidemic, which caused theaverage rates to be heavily weighted by thissingle northern epidemic. Collins (5), exam-ining data for the period 1930-45 noted thatlittle poliomyelitis had been reported from thethree southern divisions prior to 1935 but thatsubsequently they experienced "some ratherlarge epidemics." Gilliam, Hemphill, andGerende (6, 7), in a study of county rates dur-ing the period 1932-46, came to a similar con-clusion. In their study, the average annualrate in the period 1932-46 for northern countieswas 7.6 and for southern counties, 6.4. How-ever, in large urban counties of over 500,000population, average rates were lower in north-ern than in southern counties. In counties un-der 100,000 population, the reverse was true-the average rates were higher in northern thanin southern counties. The period was one ofgenerally low incidence, except for the lateryears, 1944 46. In the present study, exami-nation of rates for the 20 years 1932-51, insuccessive 5-year periods, did not seem to reflectconsistent geographic localization (fig. 2).

Public Health Reports

::..E.,..,..,. .,.'m a--,Jllj.r.'!' m, ,..

458

During the first 10 years (1932-41) of theperiod, average incidence was remarkablyuniform over 5 of the 9 major geographicdivisionis (table 4) ranging fronm 5.1 to 5.9 per100,000 population. One of these five was theEast South Central division. The lowest ratesoccurred in the West South Central and SouthAtlantic States (3.0 and 4.6) ; the highest ratesoccurred in the Mountain and Pacific divisions(6.3 and 10.7).During the first half (1942-46) of the next

decade, the northwestern divisions had rateswhich were generally higher than those of theSouth Atlantic, East South Central, and WestSouth Central divisions. However, within theeastern and southern regions, the average 5-yearrates for the New England States was some-what lower than that of the West South CentralStates.In the next 5 years (1947-51), a different con-

figuration was displayed, the divisions west ofthe Mississippi having rates considerablyhigher than those east of the Mississippi.Average 5-year rates were nearly the same, 13.4,14.0, 14.1, and 14.5 per 100,000 respectively, inthe East South Central, South Atlantic, NewEngland, and Middle Atlantic States. In inter-mediate position were the East North Centraland West South Central States with averagerates of 20.4 and 22.2 per 100,000 population.The liTest North Central, Mountain, and

Pacific States, with average 5-year rates, respec-

tively, of 28.5, 28.5, anid 26.1, were miiarkedlyhiglher than the rest of the country. For indi-vidual States, 5-year average rates are shownin table 5. It slhould be noted that the 5-yearaverage rates varied considerably among theStates in each division.Over the past 20 years geographic differen-

tials in incidence between regions of the UnitedStates have existed. In the long run, these dif-ferentials have tended to become equalized,although over rather extended time periods.Over moderate periods of time, one region mayexperience severe epidemics alternating withperiods of very low incidence, while anotherregion may be experiencing a succession ofepidemics. As a result, even longtime averagesare greatly influenced by a few severe epidemicyears.The average 20-year rates for western

geographic divisions, wlich depart most fromaverage rates of the remiiainder of the country,lhave been greatly influenced by the experienceof recent years. The marked recent rise in thewestern States generally, and particularly, inthe southwest, suggests that it may be of interestto watch the future trend in the southeasternStates which have recently had only moderateincreases in their annual rates.

Changing Epidemic Patter?ns

Interpretation of geographic differences callsfor consideration not only of average incidence,

Table 4. Average poliomyelitis case rates in each division of the United States, 1932-51, by5-year, 10-year and 20-year periods1

5-year mean

Division1932

through1936

New EnglandMiddle Atlantic --

East North CentralSouth Atlantic-East South CentralWest South Central-West North Central i_____MountainPacific

1 Average numbers of casesHealth Service.

8. 46. 03. 53. 84. 21. 52. 95. 5

14. 2

1937through1941

3. 44. 26. 75. 36. 34. 68. 17. 17. 2

1942through1946

8. 711. 611. 16. 46. 89. 9

18. 916. 614. 0

1947through1951

14. 114. 520. 414. 013. 422. 228. 528. 526. 1

th

10-year meain 20-year

1932 1942 1932Lrough through through1941 1951 1951

5.9 11.4 8.65. 1 13.1 9.15. 1 15. 7 10. 44. 6 10. 2 7. 4. 2 10.1 7. 73. 0 16. 0 9.55. 5 23. 7 14. 66. 3 22. 5 14. 410.7 20. 1 15.4

per 100,000 population based on annuial reports in Notifiable Diseases, Public

Vol. 68, No. 5, May 1953 459

Figure 3. Poliomyelitis morbidity in major geographic divisions of the United States, reportedcases per 100,000 population per annum, 1932-52.

NEW 201 I - - - * * im .ENGLAND

40MIDDLE 240 r~~-i mEmn E E mATDLALNTIC140

EAST NORTH 01:CENTRAL 204 _ Ii

SOUTHATLANTIC

EAST SOUTHCENTRAL

WEST SOUTHCENTRAL

WEST NORTHCENTRAL

MOUNTAIN

PACIFIC

20!O4n-J

00

000

wL ICawC)4

O

0

wI~-

0.bJ

2

21

40 l

4 mU-1 m~m . amm-iiI0-10

0os

I.'

ENTIRE U.S.

40

20- C0

1932 33 '34 '35 '36 '37 '3e '39 '40 '41 '42 '43 '44 '45 '46 '47YEAR

'48 '49 '50 '51 '52*

1952 PRELIMINARY NOTIFICATIONS

Public Health Reports

mi

460

but also of shiftinig centers of epidemic concen-tration. Configurations of States swept byepidemics clhange from year to year as the areasof greatest incidence move from one region toanother. Regions swept by an epidemic at onetime dissolve into components which re-form innew configurations as a succeeding epidemicwave develops.The annual concentrations of epidemics have

been illustrated excellently in the series of mapsprepared for many years by Dr. Carl C. Dauer.The first maps in this series were published inPublic Health Reports (16) and included theyears 1933-37. For subsequent years the mapshave been published yearly in an annual reviewof reported poliomyelitis in the United States.The changing centers of epidemic concentrationillustrated in detail in Dauer's series of mapscan also be recognized in the annual polio-myelitis rates (fig. 3 and table 6) for eachdivision of the United States.From 1932 through 1939, three distinctive

patterns of epidemic outbreaks emerge: TheMountain and Pacific States, which experiencedtheir most severe outbreak in 1934; the NewEngland, Middle Atlantic, and South AtlanticStates in 1935; the East South Central Statesin 1936 and 1937; and the remaining three cen-tral divisions in 1937.From 1940 through 1948, severe epidemics

did not strike east and west of the Mississippiin the same years, except for States in the EastNorth Central division, which experienced epi-demics coincident in some years with Stateseast of the Mississippi; in other years, withwestern States. In 1944, the East North Cen-tral States reflected the eastern epidemic; andin 1946, the western outbreak.In 1949, all divisions except the South

Atlantic experienced severe outbreaks of polio-myelitis. In the latter division, 1948 and 1950were years of greater severity. In 1950, rateswere moderately high in all areas.In 1951, the national rate was lower than in

the preceding 3 years. The highest rate wasrecorded in the Mountain division. In thesevere epidemic of 1952, a record rate of 98.0occurred in the West North Central States.Record rates were also reported from the otherthree central divisions and from the Mountain

Table 5. Reported cases of poliomyelitis, per100,000 population, by States, 1932-51 1

State

New England:MaineNew HampshireVermontMassachusetts ---Rhode IslandConnecticut

Middle Atlantic:New York--New Jersey-Pennsylvania

East North Central:Ohio.Indiana-Illinois-2Michigan-Wisconsin

West North Central:MinnesotaIowaMissouri-North Dakota -

South DakotaNebraskaKansas

South Atlantic:Delaware_ _-MarylandDistrict of ColumbiaVirginia-West Virginia-North Carolina -South CarolinaGeorgia-Florida

East South Central:Kentucky- -

Tennessee-Alabama.------Mississippi .

WVest South Central:Arkansas....-..-Louisiana -Oklahoma-Texas.. --

MIountain:Montana. -IdahoWyoming-Colorado-New MexicoArizona-UtahNevada_!

Pacific:WashingtonOregonCalifornia.I

1932-36

8.64.29. 39. 0

11. 36. 5

7. 75. 94. 1

3. 41. 54. 04. 82. 4

5.62. 21. 44. 63. 71. 83. 3

2. 22. 95. 57. 43. 65. 12. 12. 2.9

4.75. 24. 22. 3

1. 22. 21. 51.2

13. 38.43. 41. 53. 39. 22. 15. 1

[2. 74.5

15. 9

5-year averages

1937- 1942- 1947-41 46 51

5.0 4.8 14.93. 3 12. 4 13. 96. 4 -13.0- 15. 13. 12. 43. 3

4. 74. 03. 6

5. 56. 05. 2

11. 16. 7

11. 011. 44. 33. 16. 57. 59. 8

3. 44. 25. 04. 39. 12. 97. 47. 14. 6

5.55. 58. 26. 0

5 33. 56.73.9

6. 95. 48. 77. 86. 96. 48. 91. 9

7. 65. 37. 4

A'. XY

7. 38. 2

10. 7

14. 69. 55. 6

7.46.6

15. 38.9

14. 7

29. 511. 110. 619. 213. 617. 223. 7

12. 47.9

10. 79. 14.66. 93. 72. 97. 9

8. 66. 15. 16. 0

7. 76.5)

11. 410. 8

10. 13. 9

15. 323. 910. 812. 628. 19. 4

14. 514. 215. 5

.L . .

13. 510. 617. 1

18. 516. 58. 0

18. 814. 319. 425. 025. 6

32. 234. 414. 825. 351. 737. 626. 0

21. 912. 013. 915. 713. 520. 710. 69. 7

11. 3

14. 014. 49. 8

15. 6

21. 112. 726. 024. 0

12. 944. 333. 332. 818. 023. 535. 8.16. .5

19. 320. 929. 5

I Preliminary notifications.

Vol. 68, No. 5, May 1953

l

461

Table 6. Cases of reported poliomyelitis in major geographic divisions, 1932-52

Cases per 100,000 population

New Middle NorthEngland Atlantic CNotra

WestNorthCentral

South EastAtatcSouthAtatcCentral

WestSouthCentral

---_II I I _-II I-

2. 37. 11. 6

29. 31. 5

8. 0. 9

1. 81. 25. 2

2. 110. 59. 6

11. 310. 1

8. 24. 3

37. 113. 07. 9

14. 2

6. 77. 51. 5

13. 21. 3

4. 1. 9

6. 21. 68. 0

2. 43. 4

31. 113. 97. 1

6. 910. 125. 420. 79. 5

16. 1

1. 93. 03. 74 14. 9

8. 31. 05. 3

13. 75. 0

3. 58. 5

12. 29. 8

21. 5

11. 813. 832. 823. 819. 6

47. 7

2. 34. 92.52. 22. 7

11. 11. 37. 017.53. 8

4. 011. 59. 99. 8

59. 5

7. 238. 348. 925. 422. 8

98. 0

2. 01. 82. 2

10. 22. 8

3. 11. 85. 16. 1

10. 4

2. 01. 3

15. 26. 96. 7

5. 622. 79. 5

21. 810. 4

17. 0

1. 82. 02. 64.99. 7

6. 62. 32. 63. 4

16. 5

4. 12. 3

10. 87. 19. 5

3. 78. 6

16. 516. 721. 5

30. 0

1. 1. 4

1. 71. 82. 3

12. 41. 42. 83. 82. 4

3. 714. 93. 8

10. 716. 2

2. 717. 234. 330. 226. 7

41. 3

Moun-tain

1.42. 8

17. 92. 23. 2

9. 81. 6

12. 1

8. 73.5

3. 822. 45. 1

14. 037. 7

12. 618. 943. 317. 250. 4

51. 8

Pacific

3. 5a. a

48. 110. 55. 6

9. 11. 6

11. 49. 93. 9

2. 329. 37. 5

10. 121. 0

8. 345. 325. 823. 427. 5

38. 1

UnitedStates

3. 04. 05. 98.53.5

7. 41. 35. 67. 46. 8

3. 09. 3

14. 310.318. 4

7. 519. 12& 422. 01& 6

36. 9

SOURCE: Notifiable Diseases 1932-50 and Annual Summary in Public Health Reports, May 25, 1951, pp. 677-683.National Office of Vital Statistics: Weeklv Morbidity Reports, 1952.

States. The Pacific division experienced the Seasonal Distributionthird highest rate in its history. Along theeastern seaboard rates were well below the If the reported cases of poliomyelitis in thenational average, although moderately high in United States for each month are averaged forcomparison with many previous years. a few years, the resulting curve rises slightly in

Table 7. Seasonal incidence of poliomyelitis, United States, 1942-52

[Reported cases per 100,000 population, each month, adjusted to annual base]

Janu- Febru- MrhArlMyJn Juy Au- Sep- Oc- No- De- An-Year ary ary Marth April May Ju j July gust tern tober vein- cem- nual

her her ber Rate

1942-1.0 0.9 0.7 0.5 0.7 1. 1 3.4 6.9 8.7 6.8 3.3 2.2 3.01943 -1.3 .9 .9 .7 1.2 4.2 13.0 25.5 34.6 17. 2 8. 0 3. 2 9.31944-1.0 .9 .7 .8 1.2 3.8 19.6 47.8 49.5 25.5 10.8 4.0 14.31945-1.5 1.5 1. 1 l. 1 1.6 4.7 11.2 29.3 33.9 21.2 9.8 4.6 10.31946-1.7 1.3 1.3 1.2 2.4 & 0 25.5 65.2 52.8 34.1 14.9 6.2 18.4

1947 -- 2.4 1.6 1.2 1.0 1.3 2.2 5.6 16.1 30.4 16.3 8.0 3.3 7.51948 -- 1.4 1.0 1.0 1. 1 4.4 9.2 29.5 46.6 62.9 36.6 24.1 11.5 19.11949- 3.9 2.2 2.0 1.6 3.3 12.6 41.8 115.0 81.3 41.1 23.7 9.9 28.41950 3.7 3.4 2.9 2.1 4.0 9.1 24.0 54. 9 66. 6 49. 7 31.1 11.4 22.01951 -- 5.3 3.2 1.8 2.0 3.0 7.0 22.8 59.5 54.9 36.4 16.7 8.5 18.6

1952-..0 3.0 2.1 2.8 3.7 11.9 53.0 96.0 121.7 94.0 29.5 16.9 36.9

Preliminary notifications.

Public Health Reports

Year

19321933193419351936

19371938193919401941

19421943194419451946

19471948 ---

194919501951

1952

'I -

II~~~~~~~~~~~~~~~~~~~~~~~~~

462

Figure 4. Poliomyelitis morbidity, seasonal incidence, United States, rates by month, each year,1942-52.

5

Z 120I.-~~~~~~~~~~~~~~~~~~~~~4z0

IC

z01-

80

00 500 4

2 60z

0.

404 * ~~~1952 CUMULATED PRELIMINARY REPORTS 4

0

0.'a

JAN. FEB. I MAR. I APR. MAY JUN. JUL. AUG. I SEP. I OCT. NOV. I OEC.

May, more rapidly in June and July, andreaches a maximum elevation in August andSeptember. In October there is a marked de-cline which continues through succeedingmonths. In some years (fig. 4, table 7), Augustis the month of maximum incidence; in others,September; but in some, the attack rate has been

approximately the same in both months, forexample, the years 1944 and 1951. In two re-cent years, 1950 and 1952, the October rate hasbeen relatively higher than in earlier years.The seasonal change in incidence differs from

one region of the United States to another(fig. 5, table 8) and these differences are re-

Table 8. Seasonal incidence of poliomyelitis in major geographic divisions, 10-year average,1942-51

[Reported cases per month, per 100,000 population adjusted to annual base]

Divisions Janu- Febru- March April May June July tem-Oc No- De-ary ary g~~~~~~~~ustter ober vein- cemn

ary ary~~~~~~~~~~"~~~" h~~er to ber her

New England-1.1 0.5 0.5 0. 4 0. 5 1. 7 8. 7 41. 6 42. 7 24. 2 10.1 3.8Middle Atlantic-1. 4 .9 . 7 . 7 . 7 1. 9 11. 2 42. 2 48.2 26. 6 11. 6 4. 0East North Central- 1.1 . 8 . 6 . 5 . 7 2. 3 13.9 52. 8 57. 7 33. 8 14. 6 5. 5

South Atlantic-1. 8 1. 8 1.2 1.1 2. 4 6. 2 20. 0 31.1 27.5 16.6 9. 2 3. 7East South Central- 1. 5 1. 8 1. 3 1. 3 1. 6 6. 2 20. 7 30. 0 25. 7 15. 8 8. 6 3. 8WestSouthCentral- 3.5 2.5 2.9 2.8 8.4 22. 6 37.2 41. 1 30.4 17.8 12.3 7.0

West North Central- 2. 1 1. 5 1. 0 1. 1 1. 6 4. 4 29.5 77. 9 73. 9 44. 6 24. 1 8. 7Mountain -5.1 3. 6 3. 3 2. 4 3. 9 8. 3 25. 6 69. 7 69. 3 40.5 22. 2 12. 0Pacific -8. 0 4. 7 3. 4 2. 7 4. 9 11. 2 25. 4 48. 0 56. 5 42. 8 33. 1 17. 9

United States- 2. 3 1. 7 .1 3 1.2 2. 3 6. 2 19. 6 46. 6 47. 3 28 4 15. 1 6. 5

Vol. 68, No. 5, May 1953 463

Figure 5. Poliomyelitis morbidity, seasonal incidence, 10-year average rates by major geographicdivisions, 1942-51.

UNITED STATESWEST SOUTH CENTRAL STATESSOUTH ATLANTIC STATESEAST SOUTH CENTRAL STATES .

1942-1951

UNITED STATES

....0000-* WEST NORTH CENTRAL STATESMOUNTAIN STATES

_e- PACIFIC STATES

1942-1951

60-

50-

40-

30-

20-

10

on -.

UNITED STATES j........... NEW ENGLAND STATES

MIDDLE ATLANTIC STATES--- EAST NORTH CENTRAL STATES

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN.

1942-1951

Public Health Reports

U)U)41w-i4

n

zz49

I

z0

a-0000r0

w0-

Uj)wW

L)

aI.-

0.CLJ

IT

-4I

46i4

flected in the national curve of seasonal inci-dence as the center of epidemic intensity year-to-year moves from one area to another.In the southern divisions of the United States,

the initial rise occurs in May, reaching a maxi-mum level in August; in the central and PacificStates, the rise begins in June and the highlevels occur in August and Septenmber; and inthe northeastern divisions the rise is not appre-ciable until July, and the highest average ratesare observed in September. Generally, theepidemic span is shorter, with rise and fall morerapid, in northern latitudes.

Seasonal concentration of cases during ashort epidemic period has been characteristicof the New England, Middle Atlantic, and EastNorth Central States. In these divisions (table9), 60 percent of the year's cases, on the average,have been reported during August and Septem-ber. In the West North Central and Mountaindivisions, concentration in these months hasbeen similar but somewhat less pronounced.In these divisions, 50 to 55 percent of the totalannual number of cases were reported duringAugust and September in 1942-51.In the South Atlantic, East South Central,

and West South Central divisions, concentra-tion in August and September has been lessnoticeable. Approximately 60 percent of theyear's cases, on the average, were reported dur-ing July, August, and September. In the

Pacific States, extension of the season of hiigherincidence into the fall months has been notice-able; 40 percent of the annual total cases, on theaverage, having been reported during Augustand September, and another 30 percent of theannual totals, during October and November.

SummaryEarly descriptive accounts of poliomyelitis

outbreaks in the United States have been re-viewed and an analysis miade of State morbidityreports since 1907.

Poliomyelitis, a comaparatively rare disease inthe early years of this century, has since beenrecognized as a comm-1ulnicable disease problemnin every State in the Nation. During the last20 years the trend of the annual case rate hasbeen upward, particularly during the last dec-ade, during which a marked increase has oc-curred. The death rate has shown a slight butdefinite increase. In 1952, for the Nation, bothithe case rate and the estimated death rate werethe highest since the 1916 epidemic. The ratioof reported deaths to reported cases has de-creased over the last 20 years.

Earlier observers noticed that rates had beenhigher in the northern than in the southernregions of the country. In recent years thisdifference has diminished and an East-Westdifferential is more prominent. In recent yearsboth average and maximum rates have been

Table 9. Seasonal incidence of poliomyelitis in major geographic divisions; number of cases permonth expressed as percentage of total cases, 10-year average, 1942-51

Divisions

New EnglandMiddle Atlantic-East North Cen-

tral

South Atlantic.East South Cen-

tralWest South Cen-

tral

West North Cen-tral

MountainPacific

United States

Janu-arv

1 II I I

0. 8. 9

. 6

1. 4

1. 3

1. 9

. 81. 93. 1

1. 3

Febru-arv

0. 3. 6

. 4

1. 4

1. 4

1. 2

. 51. 21 7

March April May June Jtuly gutiSep-tem-ber

Octo-ber

0. 4. 4

. 3

1. 0

1. 1

1. 5

. 41. 31 R2

0. 3. 4

. 3

. 9

1. 1

1. 5

490

.7

1. I 1. 0 J.

.9 .8

0. 4. 5

. 4

2. 0

1. 4

4. 5

. 61. 51. 9

1. 3

1. 21. 2

1. 2

5. 0

5. 1

11. 8

1. 63. 14. 3

3. 4

6. 57. 6

7. 6

16. 5

17. 7

20. 0

11. 19. 8

10. 0

11. 1

31. 028. 5

29. 1

25. 7

25. 7

22. 1

29. 226. 618. 8

26. 4

30. 931. 6

30. 7

21. 9

21. 3

15. 8

26. 825. 621. 5

26. 0

18. 118. 0

18. 6

13. 7

13. 5

9. 5

16. 715. 416. 8

16. 1

Vol. 68, No. 5, May 1953

No-veni-ber

7. 37. 6

7. 8

7. 3

7. 1

6. 4

8. 78. 2

12. 6

8. 3

De-cemn-ber

2. 82. 7

3.0

3. 1

3.3

3.8

3.24. 67. 0

3. 7

Total

100. 0100. 0

100. 0

99. 9

100. 0

100. 0

100. 0100. 1100. 0

100. 0

I

465

hiigher in the western and north central divi-sions of the United States than in the nortlh-eastern and southeastern divisions. Overextended periods of time geographic concen-tration has not been consistent.In southern regions of the country, seasonal

rise in incidence occurs earlier and the epidemicspani is longer than in the northern regions.

REFERENCES

(1) Lavinder, C. H., Freeman, A. W., and Frost,W. H.: Epidemiologic studies of poliomyelitis inNew York City and the Northeastern UnitedStates during the year 1916. Pub. Health Bull.No. 91, Washington, D. C., Government PrintingOffice, 1918.

(2) Aycock, W. L., and Eaton, P.: Seasonal prev-alence of infantile paralysis. Seasonal varia-tion in case fatality rate. Am. J. Hyg. 4: 681-690 (1924).

(3) Aycock, W. L.: A study of the significance ofgeographic and seasonal variations in the inci-dence of poliomyelitis. J. Preventive Med. 3:245-278 (1929).

(I4) Wells, Mildred W.: Poliomyelitis. Baltimore,Md., Williams and Wilkins, 1932, pp. 306-478.

(5) Collins, S. D.: The incidence of poliomyelitisand its crippling effects, as recorded in familysurveys. Pub. Health Rep. 61: 327-355 (1946).

(6) Gilliam, A. G., Hemphill, F. M., and Gerende,J. H.: Average poliomyelitis incidence re-ported in counties of the United States, 1932-1946. Pub. Health Rep. 64: 1575-1584 (1949).

(7) Gilliam, A. G., Hemphill, F. M., and Gerende,J. H.: Poliomyelitis epidemic recurrence incounties of the United States, 1932-1946. Pub.Health Rep. 64: 1584-1595 (1949).

(8) Sabin, A. B.: Poliomyelitis. Epidemiologic pat-terns of poliomyelitis in different parts of the

world. Philadelphia, J. B. Lippincott Co., 1949,pp. 3-33.

(8) Hammon, W. McD., Coriell, L. L., and Stokes,J., Jr.: Evaluation of Red Cross gammaglobulin as a prophylactic agent for poliomye-litis. 1. Plan of controlled fleld tests and re-sults of 1951 pilot study in Utah. 2. Conduct ofearly follow-up of 1952 Texas and Iowa-Nebraska studies. J. A. M. A. 150: 739-756(1952).

(10) Hammon, W. McD., Coriell, L. L., Wehrle, P. P.,Klimt, C. R, and Stokes, J., Jr.: Evaluationof Red Cross gamma globulin as a prophylacticagent for poliomyelitis. 3. Preliminary reportof results based on clinical diagnosis. J. A.M. A. 150: 757-760 (1952).

(11) Caverly, C. S.: Notes of an epidemic of acuteanterior poliomyelitis. J. A. M. A. 26: 1-5(1896).

(12) Starr, M. A.: Epidemic infantile paralysis.J. A. M. A. 51: 112-120 (1908).

(13) Holt, L. E., and Bartlett, F. H.: The epidemi-ology of acute poliomyelitis. Am. J. M. Sc.,135: 647-662 (1908).

(14) New York Neurologic Society, Collective Investi-gation Committee: Epidemic poliomyelitis re-port on the New York epidemic of 1907. 3.Nerv. & Ment. Dis. Monograph series No. 6.1910.

(15) McClanahan, H. M.: A brief report of theNebraska epidemic of poliomyelitis. J. A. M. A.55: 1160-1162 (1910).

(16) Dauer, C. C.: Studies on the epidemiology ofpoliomyelitis. Pub. Health Rep.: 53: 1003-1020(1938); 54: 857-862 (1939); 55: 955-961(1940); 56: 875-883 (1941); 57: 710-716(1942); 58: 937-949 (1943); 59: 712-719(1944); 60: 633-642 (1945); 61: 915-921(1946); 62: 901-909 (1947); 63: 393-396(1948); 64: 733-740 (1949); 65: 78Z-787(1950); 66: 673-684 (1951); 67: 524-526(1952).

Type I Poliomyelitis Virus Adapted to MiceSuccessful adaptation of type I (Mahoney) poliomyelitis virus to Swiss

mice has been achieved by Drs. C. P. Li and Morris Schaeffer of the PublicHealth Service Communicable Disease Center. Their report appears in theMarch 1953 issue of the Proceedings of the Society of Experimental Biologyand Medicine, pages 477-481.

The authors conclude that: "The use of the intraspinal route of inoculationand the selection of a mutant or variant of the virus is believed to be responsiblefor this adaptation. . . . With this attainment, all three poliomyelitis viruistypes hlave now been adapted to mice. This will permit for rapid progress infield and laboratory studies of poliomyelitis." The findings are important topoliomyelitis diapgosis and to the development of a live virus vaccine.

466 Public Health Reports