Seroepidemiological Study on Rubella at Yaeyama Archipelago, Okinawa Prefecture

Abstract

From 1972 to 1974, HI antibody titer against rubella virus among the inhabitants was evaluated in Ishigaki, Iriomote, Kuroshima, Aragusuku and Yonaguni islands of Yaeyama archipelago, Okinawa Prefecture. The date of onset, size and other charateristics of the rubella epidemics in the past was retrospectively inferred by the date on the rates of the antibody positive individuals among each age groups of the islanders. The antibody positive infants were few im number, and the occurrence was sporadic in the communities throughout the archipelago. While the rate of the positive individuals was about 30 per cent among the younger school-children, it leaped to such a high level as 80 per cent or more in the older classes. This age of the leap was variable among the communities depending on their demographic, geological and social conditions, ranging 7 to 10 years of age. It is presumed that such a variance of leaping age in each communities reflects the course of the rubella epidemics which invaded Okinawa island in 1964 and then propagated southward to the Yaeyama archipelago.