REINHARD 



cent, Type 2,92 per cent, and Type 3, 62 per cent. Except for cen- 

 tral Alaska (Fort Yukon) and St. Paul Island, the prevalencies of 

 T3T)es 1 and 2 were similar throughout. Antibodies against Type 3, 

 which is generally the rarer of the three known poliovirus type^, 

 tended to decrease with increasing geographic latitude and conse- 

 quent decreasing population density. 



Figure 2 summarizes the results of a serological cross- sectional 

 study of the population of St, Lawrence Island. Noticeable in this 

 study were (1) the high prevalence of Type 2 antibodies in the chil- 

 dren, (2) the apparent reciprocal relationship between decline in 

 prevalence of Type 2 antibody and increase in Types 1 and 3, and 

 (3) the uniformly high prevalence of antibodies to all three types in 

 the advanced age groups. The results indicated that polioviruses 

 have been endemic, Type 2 more so than Types 1 and 3, and that this 

 situation may have existed for many years. 



The epidemiological experiences and serological studies showed, 

 therefore, that Alaskan natives were generally highly immune to 

 polioviruses. Indeed, Alaskan natives appeared to be much more 

 experienced with polioviruses than the urban, non- native Alaskan 

 population. One might speculate, with good reason, that the urban 

 Alaskan epidemics of 19 53-54 and earlier years might have been de- 

 rived from endemic foci in the villages. A relatively higher immunity 

 among natives as compared with non- natives was also found by 

 Adamson and associates in a study of a poliomyelitis epidemic in 

 Whitehorse, Y.T. (19 54). Sero- epidemiological studies by Hildes, 

 Wilt and Stackiw (19 59) indicate current development of immunity 

 against polioviruses among eastern Canadian natives. 



The poliovirus studies stiumlated cultural work on the ecology 

 of enteroviruses generally (Reinhard, 1961). Table II presents the 

 results of virological culture of series of stool samples from the 

 residents of native villages. The samplings for these virological 

 surveys were taken opportunistically, as facilitated by field work 

 for the study of other problems. Yet these random surveys yielded 

 a large number of enteroviral isolates. The Napaskiak-Oscarville 

 series are particularly significant because of the large variety of 

 types isolated, the wintertime epidemic of infection, and the long 

 persistence of these agents in so small a population group. The 

 samples from Ft. Yukon in September 19 58, and St. Lawrence Island 



56 



