ln 1966 two expeditions were made tothe Tiriyo, an lndian tribe on the Brazil-Surinam border, and gera were collectedírom 180 oí the estimated 700 tribalmembers. Serologic studies indicated thatthese

lndians had not been affected bycertain oí our commonest viruses. Similarserologic studies have been made oí iso-lated populations in Colombia (1), NewGuinea (2), Micronesia (3), Tristan daCunha (4), central Brazil (5) and sev-eral other areas (6). None oí these otherstudies covered entirely the garoe spectrumoí viroses, but it seems clear the Tiriyo

had a lower antibody prevalence to manyacute viroses than any group previouslystudied.

Throughout most of man's evolutionaryhistory he lived in small bands as theTiriyo do now. Epidemiologic studies ofisolated populations suggest that certainviroses would not be maintained inthese small bands and must have evolvedmore recently (7, 8). The present serumcollection offered an opportunity toidentify some of the viroses which couldperpetuate themselves under these condi-tions and, hence, might be implicated" aspossible ecological elements in the de-velopment of the human species.

The locale. Details of the Tiriyo peopleand culture have been published elsewhere(9, 10). Circumstances contributing totheir isolation are particularly pertinenthere. The Tiriyo territory is about 500 kmnorth of the Amazon River on the Tumuc-umhac mountains. Because of its eleva-tion, rivers draining the area are swiftwith many rapids and access by canoe is

1 Portions of this investigation have been sup-ported by grants AI-OO701, PH-43-68-1037 and

PH-43-66-477 from the U. S. Public HealthService, a grant from The Rockefeller Founda-tion and CCOO242 from the National Com-municable Disease Center.

.Department of Epidemiology and PublicHealth, Yale University, New Haven, Conn.06510.

.The Rockefeller Foundation Laboratory atBelém, ~ará, Brazil.

.Children's Hospital, Philadelphia, Pa.

430

AMEBICAN JOUBNAL 01' EPIDEKIOLOGY Vol. 91, No. 4Copyrigbt @ 1970 by Tbe Jobns H!>pkins University Printed in U.8.A.

PREV ALENCE OF ANTIBODY AGAINST VIR USES IN THETIRIYO, AN ISOLATED AMAZON TRIBEl

F. L. BLACK', J. P. WOODALL8, A. S. EV ANS', H. LIEBHABER'AND GEMRUDE HENLE'

Black, F. l. (Dept. Epidemiology and Public Health, Vale Univ. School of Medi-tine, New Haven, Conn. 06510), J. P. Woodall, A. S. Evans, H. liebhaber andGertrude Henle. Prevalence of antibody against viruses in the Tiriyo, an isolatedAmazontribe. Amer. J. Epid., 1970, 91: 430-438.-An isolated primitive popula-tion that has an unusually low rate of serologic reactions against several of thecommon acute viral infections has been identified in northern Brazil. The preva-lente and distribution of antibodies against 38 different viruses have been com-pared in sera from this population. Except for rubella and poliovirus, those virusesthat cause infections of limited duration seemed to have had very little currencyin this population. On the other hand, the herpes group viruses and adenoviruseshad affected the majority. Arbovirus antibodies were frequently found in adults,especially against Mayaro and yellow fever.

antibodies; arbovirus; herpesvirus; influenza; measles; rubella; serology; vírus

diseases

(Received for publication October 9, 1969)

VlRAL ANTIBODIES IN AN ISOLATED TRIBE

seen. The priests had seen no evidence ofvaricella, there were no smallpox scars,and tuberculin reactions were alI negative.

METHODS

very difficult. When the tribe was firstcontacted by P. Frikel in 1951, they livedin 30-40 settlements scattered over a mixedforest and savannah area of about 4,000km2.

The Tiriyo have been cannibalistic andrelationships with neighboring tribes weremostly hostile. Some trade was conductedwith the Bush Negro. One negroid womanin the village was said to have beenbrought as a child captive from a BushNegro group, and other women may algohave entered the tribe through capture.

ln recent years, two missionary groupshave established contact with the Tiriyolndians. ln Surinam, a Protestant missionin Bush Negro territory has extended itsinterests to this tribe. Seven days walkaway from the Protestant mission, theFranciscans have established a small mis-sion in the Brazilian pari of the Tiriyoterritory. The Franciscan mission is sup-plied by the Brazilian Air Force, whichstages flights about once a month to anairstrip built in 1961. The flight crew oftenspends the night at this base. A Brazilianpeasant family, hired by the mission, anda family from the Iieighboring Kaxuyanatribe have moved to the mission. A con-siderable village has grown up aroundthe Brazi.lian mission, and the serum speci-mens used in this study were taken frompersons living in or coming to this village.

Histories were difficult to obtain not onlybecause of the language barrier and thelndians' disinterest in past disease, butalgo because they had no system of num-bers and hence no way of counting years.AlI ages over two were estimates. Tenlndians had been flown out to urban areasfor medica I treatment in the tive yearspreceding the study. One man of about30 had flaccid paralysis of the .left arm,said to have developed while visiting atthe Surinam mission. The Franciscans re-ported that there had been an extensiveruQella epidemic about 1962, but no evi-dence of congenital rubella syndrome was

SeTa. Blood specimens were collected inApril of 1966 and again in November andin December. After clotting and retrac-tion, the sera were poured off. They werestored at -200 until testing, but heldinitially for a few weeks at 5°.

Inftuenza and parainftuenza hentaggluti-nin inhibition. The microtiter method ofSever (11) was used. AlI sera were in-activated at 560 for 30 minutes and treatedwith KIO4 and trypsin to remove non-specific inhibitors. For parainfluenza tests,the sera were further absorbed with packedguinea pig red blood cells. Four HA anti-gen units were employed. Positive andnegative control sera were included ineach run and alI titer rises were con-firmed by repetition. Antigens were sup-plied through the kindness of the NODO.The influenza strains used were: A/PR8/1934, A2 Japan/170/1962, B;Taiwan/2/1962 and B/GL/1739/1954.

M easles and mumps.. HI tests were car-ried out as described previously (12),using kaolin extraction of sera and Cerco-pithecus mitis red blood cells in the testsystem. Measles antigen was a live tissueculture grown virus suspension; mumps an-tigen was a commercial preparation (mumpsviral OF antigen, Microbiological As-sociates,Bethesda).

Rubella. HI tests were done by a modifi-catioft of Feldman's method (13). In thesetests sera were pretreated with onetwelfth volume 5 per cent dextran sulfateand then one-sixth volume M OaO)2 in-stead of as in the original procedure.

Poliomyelitis. Neutralization was testedas previausly described (14) in Veroserial diploid monkey kidney culture usingthe LSc, YSK and Saukett strains for viruschallenge and a single serum dilution of1/4.

432 BLACK, WOODALL, EVANS, LIEBHABER AND HENLE

Herpes. Neutralization tests were madeusing 100 TCD5o of a Type I strain as chal-lenge, a one hour incubation of vírus withserum at room temperature and Rep-2culture as the test system. Plaque reduc-tion tests were carried out by the methodof Rawls et aI. (15), using the Shealey(Type I) and Recks (Type 2) strains fromDr. Andre N ahmias as challenge vírus.

Epstein-Barr virus (EBV). Antibodieswere determined by indirect immunofluo-rescence as describedpreviously (16).

Varicella and cytomegalo. Complementfixing antibodies were measured by Mi-crobiological Associates viral diagnosticservices.

Adenovirus. Immunoprecipitins were de-termined by double diffusion in 1 per centagar. A commercial complement-fixing anti-gen (Microbiological Associates lot 3-2254)was placed in the center well and undilutedserum in peripheral wells.

The plates were stained with thiazinered R at 72 hours and examined forbands.

Arbovirus. RI antibodies were measuredas described by Shope and Causey (17).Nineteen different vírus antigens weretested: Group A-Eastern equine enceph-alomyelitis, Mucambo, Pixuna, Una, Auraand Western equine encephalomyelitis ;Group B-yellow rever, Ilheus, Bussuquaraand St. Louis encephalomyelitis; Bunyam-wera group-Maguari and Guaroa; Phle-botomus rever group-Candiru, Icoaraci,Bujaru and Itap~ranga (18); AnophelesA group-Tacaiuma; Simbu group-Utinga(18).

RESULTS

V iruses a8sociated with acuteinfections (figure 1)

Inftuenza. Only one individual testedpossessed HI antibody against the PR8strain of Influenza A. This was a womanof estimated 35 years who had a titer of80 in two specimens collected three weeks

apart.. There was no history to suggest thesource of her exposure.

Five persons, alI adult and falir of themwomen, had A2 HI antibody at a titer of10 or more. Only one of these personshad been out to an urbanized area.

There was no evidence of Type B minfluenza antibody against either of twotype B strains.

M umps and parainfluenza. A numberof the adults and adolescents had mumpsand parainfluenza (especially type 3) HIantibodies. The proportion positive (i.e.~10), however, was much lower than hasbeen found in other populations (6). Themean titers of positive specimens alsowere lower than has been found in otherpopulations: the geometric mean of positiveTiriyo mumps. titers was 11 and mean .ofparainfluenza 3 titers was 25. There wassome association of distribution of anti-bodies against these viruses; whereas only23 per cent of the entire population hadmumps HI antibody at a titer of 10 ormore, 60 per cent of those with parainflu-enza 3 antibody were mumps positive.

Shortly after arrival of the November-December expedition at Tiriyo, a generallynon-febrile upper respiratory illness withcoryza and cough broke out and involvedessentially the whole village. Five of 66seru~ pairs collected before and after thisepidemic showed a fourfold or more in-crease in parainfluenza 3 HI titer and 13others showed a twofold increase. Only onepair was recorded as showing a twofolddecrease. AlI but one of these pairs hadmeasurable antibody in the pre-epidemicspecimen. In the mumps series there wasno titer change of more than twofold.

M easles. Like A2 influenza, measlesantibodies were confined to a few adultsand adolescents. No one individual hadantibody to both measles and influenza, Dordid the measles immune group correlatewith those who had visited urban areas.

Rubella. Rubella HI antibodies were

0- 10- 25- 35- 45+ O- 10- 25- 35- 45+ O- 10- 25- 35- 45+AGE 9 20 30 40 9 20 30 40 9 20 30 40

I I I I I I 1 I I I I I I I I I I

100

INFLUENZA INFLUENZA INFlUENZA BkI PR 8 A TAIWAN GREAT,LAKE S~ aI-

üi 50 TAIWANoIl.

~.o

NO. TESTED100

PARAINFLUENZA 2kI>I-üi 50oIl.

~.NO. TESTED o

100

kI>I-üi 50oQ,

~

ONO. TESTED

100

kI>I-

üi 5oIl.

at

ONO. TESTED 15

FIGURE 1. Prevalence of antibody in Tiriyo Indiana by age group. Viruses usually asso-ciated with acute limited infections.

found in alI gera tested, with the excep- groups. However, an undetermined buttiQn of five children, three years old or reportedly small number of doses of liveyounger. Only one child under three years poliomyelitis vaccine was distributed ingave a positive reaction, and one estimated the village prior to collection of the gera.at three years of age was algo positive. Because the vaccine recipients were notTiters of positive gera seemed to be higher identified and secondary spread could notthan in persons of comparable age in the be estimated, little significance can beUSA, but the quantitative comparability placed on the poliomyelitis data with re-of the testa was not confirmed. spect to natural infection. The man with

Poliovirus. AlI three types of poliovirus the paralyzed arm had Type 2 poliomye-antib.ody were frequently found in alI age litis antibody only.

VIRAL ANTIBODIES IN AN ISOLATED TRIBE 433

434 BLACK, WOODALL, EVANS, LIEBHABER AND HENLE

ferent parts of the viII age. The largefamily of the chief and two neighboringfamilies lacked measurable varicélla anti-body. The Kaxuyana family lacked EBVantibody.

Adenovirus. Immuno-precipitin reactionswere positive in nearly alI the gera tested.No attempt was made to resolve thisin terms of the types of adenovirus in-volved.

Viruses transmitted by arthropods(figure 2)

Group A. Sixty per cent of th~ sampletested had HI antibody in a titer of 10 ormore against at least one Group A Toga-virus. In most instances, this was confinedto the Mayaro-Una subgroup (table 1),with the Mayaro titer highest, but broadreactions against most or alI the Group Aantigens tested were also encountered. Itis difficult to say what viroses mar havebeen responsible for broadening the re-sponses, but in two instances the onlypositive reactions were against Pixuna andMucambo" and one of these or the related

Viroses associated with chronicinfection (figure 2)

Herpes. A strong age correlation wasseen in the distribution of herpes anti-body, with no positive reactions in chil-dren under tive years and only two nega-tive reactions in persons over 12. Plaquereduction tests gave positive results (K >4.0) in eight of 14 sera tested against Type1 herpesvirus, but only one of 14 testedagainst Type 2. In each instance, Type 1titers were at least as high as Type 2,and the average Type 1 titer was threefoldhigher than Type 2.

Other herpes-group viroses. EB, varicellaand cytomegalo-virus antibodies werepresent in large proporlion of the seratested. Many of the positive reactions wereat the lowest leveI considered significant,and it is probable that a proportion ofthose reactions recorded as negative actu-ally had antibody at titers below thethreshold recognized. No age correlationwas found in the distribution of any ofthese antibodies, but both EB and vari-cella had an uneven distribution in dif-

FIGURE 2. Prevalence of antibody in Tiriyo Indians by age group. Viroses associated withpersistent infection and viruses transInitted by arthropods. Data for the arboviroses are thetotal number positive against any tested vinIS of the group.

0- 10- 25- 35- 450 0- 10- 25- 35- 4510 0- /0- 25- 35- 45+ 0- 10- 25- 35- 45+9 20 30 40 9 20 30 40 9 20 30 40 9 20 30 40

AGE I I I I I I I II I I I I I I I I I I I I I

100 ::::::::::::~:~:~:~:~:~:~~~~~~~~~~~~~~~~[~[~~~~~~ EB VIRUS-F.A. VARICELLA C.F. CYTOMEGALO C.F.

\IJ>I-üi 50oa.

~O

NO. TESTED~ 100 ti.~ BUNGY:~UW:RA

J ':t-NO. TESTED 9 4Z 39 47 33 17

TABLE 2

Age and sex distribution oJ titers oJ 10 or nwre

against one or nwre antigen oJ Togavirus GroupA orB

Venezuelan equine encephalomyelitis virusmay have been active in the area. Only onechild under 10 years had Gr~p A anti-body, but antibodies seemed to have beenrapidly acquired with maturity and theprevalence in upper age groups was high.Rates in males were somewhat higher thanin females with 71 per cent of the malesand 51 per cent of the females positive forone or more Group A antibody (table 2).

Group B. The overall prevalence ofGroup B Togavirus antibodies titrating 10or higher was nearly the same as GroupA, but more children had antibody to oneor more of these viroses and they were notquite so prevalent in older adults (figure2). Yellow rever antibody was the mem-ber of Group B most frequently encoun-tered (table 1). No vaccine had been usedand this must be attributed to naturalinfection. Eight per cent of the populationhad antibody to the llheus-Bussuquara-St.Louis subgroup without yellow fever.llheus titers were usually the highest of

these. The Group B antibody preva-lence showed sex differential very similarto that observed with Group A (table2).

Other arboviruses. Eight arbovirus anti-gens outside Group A and B were testedagainst these gera. Positive titers weregenerally low (10 or 20) and not alwaysreproducible in serial serem specimens.Only titers oí 20 or more are recorded intable 1 or figure 2. No titer over 10 was

.Specimens in which only Mayaro and Una HI were positive or in which one of them (almost alwaysMaya.ro) was fourfold or more higher than anyother.

t Specimens without yellow rever HI but with Ilheus, Bussuquara and/or St. Louis encephalitillIlheus HI was most often the highest titer.

VIRAL ANTIBODIES IN AN ISOLA'fED TRIBE 435

TABLE 1

Antibody against viruses transmitted by arthropods-per cent 01 sample positive

Ale o-.f 5-9 16-20 21-JO J1~.1 &; OverTotal

118No. Tested .6 26 39 41' 33 11

Group VirusA Mayaro. O 4 41 57 79 76 47

Pixuna O O 2 2 O O 1Multiple O O 18 15 18 12 12

Yellow rever O 12 20 13 18 12 14Ilheust O 12 10 11 6 6 8Multiple O 12 33 45 52 65 35

Bunyamwera Guaroa O O O 8 24 29 10Maguari O O 8 6 O O 4

Phlebotomus Bujaru O O 5 6 6 6 4Itaporanga O 8 O O 3 O 2

Anoph. A Tacaiuma O O 2 O O 24 3

Ale 0-1. 15-30 Over 30 Total

Su M F M F M F M F

No. 27 JO 35 35 2J 28 85 93

Group A 26 13 86 62 100 89 71 51

Group B 48 17 72 63 91 64 69 48

~

outside the tribal boundaries. li the viroseshad actually reached the Tiriyo in theirown territory, one would expect that, likerobella, they would have elicited veryhigh incidence of antibody responses.Brown et aI. (3) found that alI the sus-ceptible population of certain Micro-nesian islands converted to A2 positivereactions after an A2 influenza epidemic.Similarly high conversion rates have beenseen after poliomyelitis (20) and measlesepidemics (2, 21). Apparently there wasno reactivation of any of these virosesfrom a latent state in the recovered in-dividuaIs, for that, too, would have touchedoff a generalized epidemic.

The prevalence of HI antibody to robellaconfirms the history of an epidemic aboutthree years prior to testing. The numberof children bom since the epidemiç andincluded in the test was small and thetime relatively short, so it is difficult tosay if the viros might have persisted iri thecommunity. Every adult serom tested hadantibody, suggesting that the epidemic hadreached alI or nearly alI of the susceptible.persons livrng at that time.

The picture presented by the herpes-viros group is very different from that ofthe acute viral infections. Antibody tothese viroses was very widespread and,except for herpes simplex, uniformly dis-tributed in alI age groups, suggestingthat many infections occurred very earlyin life. No explanation has' been found lorthe age cut-off in the herpes antibody,which is usualIy algo acquired early inlife in other populations. While Type 2herpes could not be eliminated, TYpe 1seemed definitely to have been presentand, hence, there was no reason to sup-pose transmission was dependent on vene-real spread. AlI these viroses arE! char-acterized by chronic infections, and herpesand varicelIa are known to be recurrentlyinfectious. The suggestion is that EBV andcytomegaloviros may algo reactivate fromtime to time, and that this offers common

found to Candiru, Icoaroci, or Utinga. Re-actions to the other viroses were not en-countered with great frequency, but theyseemed at least as prevalent in the Tiriyoas in other Amerindian populations (5).There may have been different prevalencesof certain viroses in different age groups,but the number of reactions was too smallto lend much significance to these varia-tions.

DISCUSSION

Th~ prevalence of antibodies againstthe acute viTal infections was much lowerin the Tiriyo than in other South Americanpopulations (14, 19) and lower than inmany other relatively isolated populations(6). This low prevalence of these commonvírus antibodies tends to confirm the im-pression that this tribe was unusually iso-lated. No population, except perhaps onselected atolls in the Carolines (3), hasbeen found to present so little evidence ofexposure to the influenza viroses.

The amount of mumps and parainflu-enza antibody in these seTa was strikinglylow both in incidence and in titer. More-over, these antibodies are not entirelyspecific for the type of infecting vírus, andit is possible that the observed reactionswere alI elicited by only one or two ofthe tested viroses, or even to types notincluded in the tests. The fact that mostincreases in parainfluenza titer, during theperiod of upper respiratory disease, oc-curred in persons with some pre-existingantibody suggests that they were due tocross reactions with some such untested

type.It is significant that, although anti-

bodies to most viTal infections were rare,there was evidence that most of theseviroses had each reached a few membersof the tribe and that, nevertheless, therehad been no general epidemic. It seemsprobable that these occasional infectionsoccurred in individuaIs living or traveling

436 BLACK, WOODALL, EVANS, LIEBHABER AND HENLE

437VIRAL ANTIBODIES IN AN ISOLATED TEmE

mechanisms for maintenance of the virosesin the community.

Much the same can be said for theadenoviruses, which are known to persistin lymphoid tissue. As a group, they, too,seem to have had a high prevalence in thisisolated population.

The isolation of the Tiriyo does notapply to the arboviruses. These agentshave other hosts, both arthropod andwarm-blooded, that provide a continuumof susceptible organisms over wide ecologi-cal areas quite independent of humanpopulations. The prevalence of arbovirusantibodies in the Tiriyo was high, butthis might have been anticipated from thedegree of exposure to mosquitoes and theprevalence of other hosts for the viroses.

In general, the isolation of the Tiriyodid not prevent most viroses from reachingat least some members of the tribe. Thoseviroses that cause only acute infectionswere not carried back to the tribe, or, ifthey were, they seem to have consumedthe available susceptibles quickly and thendied out. Viroses that cause chronic infec-tions with persistence of the infectious agentwere as prevalent among the Tiriyo asamong less isolated populations.

REFERENCES

1. Weir, J. M. The incidence of protective anti-bodies against influenza A and B amongthe Cubillo Indians of the Vau pés Terri-tory, Columbia. Amer. J. Hyg., 1945, 41:137-142.

2. Adels, B. R., Francis, J. E., Jr. and Gajdusek,D. C. Measles in Australasian Indigenes.Amer. J. Dis. Child., 1962,103: 255-260.

3. Brôwn, P., Gajdusek, D. C. and Morris,J. A. Epidemic A. influenza in isolatedPacific island populations without pre-epidemic antibody to influenza virus typesA and B, and discovery of other still un-exposed populations. Amer. J. Epid., 1966,83: 176-188.

4. Tyrrell, D. A. J., Peto, M. and King, N.Serological studies on infections by respira-tory viroses of the inhabitants of Tristanda Cunha. J. Hyg. Camb., 1967, 66: 327-341.

5. Neel, J. V., Andrade, A. H. P., Browli, G. E.,Eveland, W. E., Goodbar, J., Sodeman,W. A., Jr., Stollerman, G. H., Weinstein,E. D. and Wheeler, A. H. Further studieson the Xavante Indians. IX. Immunologicstatus with respect to various diseases andorganisms. Amer. J. Trop. Med Hyg.,1968, 17: 486-498.

6. Brown, P. K. and Taylor-Robinson, D. Res-piratory vires antibodies in sera oí personsliving in isolated communities. Bull.W.H.O., 1966,34: 895-900.

7. Hope-Simpson, R. E. The nature oí herpeszoster: a long-term study and a new hy-pothesis. Proc. Roy. Soe. Med., 1965, 68:9-20.

8. Black, F. L. Measles endemicity in insularpopulations: Critica! community size andits evolutionary implication. J. Theor. Biol.,1966,11: 207-211.

9. Frikel, P. Fases culturais e aculturacao in-tertriba! no tumucumaque. Boletin do MuseuParaense Emilio Goeldi, Belem, 1961,16.

10. Black, F. L., Wooda!l, J. P. and Pinheiro,F. de P. Measles vaccine reactions in avirgin population. Amer. J. Epid., 1969,89: 168-175.

11. Sever, J. H. Application oí a microtiter tech-roque to serologica! investigations. J. Im-munol., 1962, 88: 320-329.

12. Black, F. L., A nationwide survey oí U. S.military recruits, 1962. m. Measles andmumps antibodies. Amer. J. Hyg., 1964,80: 304-307.13.

Liebhaber, H. The measurement oí rubella an-tibody by hemagglutination-inhibition. li.Characteristics oí an improved HA-I testemploying a new method for the remova! oínon-immunoglobulin HA inhibitors írom se-rum. J. Immunol., 1970,104: in press.

14. Niederman, J. C., Henderson, J. R., Opton,E. M., Black, F. L. and Skvrnova, K. Anationwide serem survey oí Brazilian mili-tary recruits, 1964. li. Antibody patternswith arboviruses, polia viroses, measlesand mumps. Amer. J. Epid., 1967, 86: 319-329.

15. Rawls, W. E., Tomkins, W. A. F., Figueroa,M. E. and Melnick, J. L. Herpes type 2:Association with carcinoma oí the cervix.Science, 1968, 161: 1255-1256.

16. Henle, G., Henle, W. and DieW, V. Relationoí Burkitt's tumor-associated herpes-typevires to infectious mononucleosis. Proc.Nat!. Acad. Se., 1968,69: 94-101.

17. Shope, R. E. and Causey, O. R. Furtherstudies on the serologica! relationships oí

438 BLACK, WOODALL, EVANS, LIEBHABER AND HENLE

Group C arthropod-borne viroses and the arboviruses, polioviruses, respiratory viroses,application oi these relationships to rapid tetanus and treponematosis. Amer. J.identification oi types. Amer. J. Trop. Med. Epid., 1969,90: 292-303.Hyg., 1962,11: 283-290. 20. Paul, J. R., Riordan, J. T. and Melnick,

18. Taylor, R. M. Catalogue oi Arthropod-Borne J. L. Antibodies to three different anti-Viroses oi the World. U. S. Public Health genic types oi poliomyelitis virus in geraService Publication No. 1760, 1967. irom North Alaskan Eskimos. Amer. J.

19. Evans, A. S., Casals, J., Opton, E. M., Hyg., 1951,54: 275-285.Borman, E. K., Levine, L. and Cuadrado, 21. Black, F. L. and Rosen, L., Patterns oiR. R. A nationwide serem survey oi Colom- measles antibodies in residents oi Tahitibian military recruits, 1966. I. Description and their stability in the absence oi re-oi sample and antibody patterns with exposure. J. lmmunol., 1962,88: 725-731.