Preliminary Report of Epidemiological Studies on Poliomyelitis and Streptococcal Infections

Abstract

Serological surveys were undertaken in an attempt to obtain data of epidemiological significance in respect to the factors underlying differences in age distribution of poliomyelitis. Sera of normal children over a range of ages were obtained from numerous widely separated areas and countries. Within 3 California cities 2 distinctly different economic groups were sampled. Sera were tested for Lansing poliomyelitis antibodies and antistreptolysin "O." There was no indication of any antigenic relationship between the streptococcus and this poliomyelitis virus. Antibodies of both types tended to develop latest in life in California cities and at an earlier age in southern U. S. cities, subtropical and tropical areas, respectively. In the California cities the proportion of positives tended to decrease or remain at a constant level after 6-9 yrs. of age, suggesting that antibodies to both agents were temporary and required, to maintain an elevated level, repeated and frequent reinfection such as that acquired most commonly through the contacts of young children. In the 3 cities where separate economic groups were studied, the antibody to both agents developed earlier in the lower economic groups than in the upper. Because family size was observed to hold an inverse relationship with economic level in these areas, family size and the incidence of infection, as observed in antibody tests, were examined within each economic group. Number of children in the family was found to correlate directly with the proportion having antibodies to each type of organism. The opportunity of having infection introduced into a family increases with the number of children. Infection appears to spread readily within the family, due probably to the type of intimate contact. Differences in family size may explain, in part at least, the apparent changing age trends shown by poliomyelitis in the northern U. S. and elsewhere, as well as the early age of infected children still observed in the south, the subtropics and the tropics. Birth control and the relative isolation of small family units may be more important in postponing the age of infection than developments in sanitation, or any other factor involved in the progress of modern civilization. Schools probably help to neutralize this age trend in other diseases which are readily air-borne, such as measles and chicken pox, but are possibly less likely to contribute greatly to the spread of the streptococcus and poliomyelitis, where more intimate contact appears to be essential. Poliomyelitis along ordinarily occurs during school vacation periods and thus may be even more dependent on family contact type of spread. All analyses of the 1400 sera included in this report are of a preliminary nature. Tentative conclusions are suggested indicating the trend for extension of this type of study to obtain more specific and more reliable data.