A Seroepidemiological Observation of Rubella by Survey on Sera of Pregnant Womenin Kawasaki

Sera of 1740 pregnant women, aged 18 to 38, were collected at Kawasaki city from October 1970 to October 1971, and HI antibodies to rubella, were examined for seroepidemiological study: For comparison, the sera were divided in groups, by age of donor, by district where the donors wereliving, and by season when the samples were collected, and the data obtained were statistically analysedin age distribution, regional differences, and seasonal fluctuation. The negative rates were almost equal between northern and southern districts, and among fourseasons. They varied among age groups, that is, the younger the age, the higher rates were obtained. The distribution of antibody titers of all positive sera showed normal curve with a peak of 26-intiter, and the mean titer was approximately 6 (log 2). In comparison of seasonal fluctuation, the averagetiter of autumnal group was the lowest among four groups, and it increased in winter and spring. Thetendency was distinct in northern districts. The incidences of abnormally high titer donor were alsohigher in winter and spring. It was suggested that a sizable endemic of rubella might have occurredduring the time between the end of winter in 1970 and spring in 1971 in Kawasaki city.