Ecological Behavior of 6 Coxsackie B and 29 Echo Serotypes as Revealed by Serologic Survey of General Population in Aomori, Japan

Neutralizing antibody titers of 252 random serum samples from different age groups were determined by the microplate method. The results showed marked differences in the grade and pattern of dissemination among the serotypes. Echo-22 (Group I) showed extremely high endemicity with an infection rate higher than 50% among infants within the first year of life. Cox B-1, 3, and 4 and Echo-9, 11, 14, 21, 25, and 31 (Group II) were highly endemic with occasional outbreaks. Cox B-2 and Echo-3, 4, 6, 12, 13, 15, 16, 19, 20, 26, and 29 (Group III) showed relatively low endemicity with extensive dissemination at relatively long intervals. Cox B-5 and Echo-7 (Group IV) gave unique antibody-incidence curves with a sharp peak at a certain age, which was explained by extensive spread of virus in a certain year after many quiescent years and a strong age preference of primary infection for young children. Echo-2, 17, 18, 24, 30, and 33 (Group V) maintained low endemicity with no extensive dissemination. Cox B-6 and Echo-1, 5, 27, and 32 (Group VI) showed the lowest endemicity. Long communicable periods of the infected host seem to be a decisive factor for Groups I and II to maintain the high endemicity, and the possibility of intrauterine or neonatal infection was suggested for Echo-22 in particular. The chronic carrier state was suggested for the very low endemic serotypes to secure continuous transmission.