A serological survey of antibodies to all three types of poliomyelitis virus has been carried out in an urban and semiurban population in French Morocco. The rates at which neutralizing antibodies and complement-fixing antibodies have been acquired by this population according to different age groups are herein reported.
Heavy infection and a rapid development of antibodies at an early age characterize the pattern obtained. The results indicate the presence of actively acquired neutralizing antibodies, and presumably immunity, to all three types of poliomyelitis virus in about 80 per cent of the population by the time children have reached 5 years of age. The percentages persist in all older age groups. Complement-fixing antibodies, on the other hand, are present largely in the juvenile population, and fall to low levels in those over 10 years of age. Since the complement fixing antibody in poliomyelitis is a transient one, this suggests that active infection is occurring only in young children in the Moroccan population.
As a control disease, presumably spread by human association, mumps was selected, and antibody patterns to mumps virus were determined. Results indicate that mumps infection also comes early to this population but in so far as a comparison is warranted, apparently not as early as does poliomyelitis virus infection.
The findings differ sharply from those which might be expected from a United States city studied at about the same latitude. Their interpretation has some bearing on the relationship between antibody and immunity in the infant, pointing to a close relationship between the two. The results also point to the fact that living conditions in this population are apparently particularly conducive to the spread of infantile infections with both poliomyelitis and mumps but particularly the former.