Yearly successive epidemics of rubella occurred in 1967 and 1968 among recruits of the Japanese Ground Self-Defence Forces (JGSDF) at Ohtsu Base Camps in Ohtsu city. The perpetuation of rubella virus was suspected in such a closed population as that of base camps of JGSDF.
In order to clarify the facts, monthly surveys of sera of recruits of the base were successively carried out for about three years starting from the end of June in 1968 when the second epidemic was over.
The following results were obtained from the surveys.
1) The positive rates of antibody to rubella virus varied from 60 to 90% in sera of the recruits which were collected at the enlistment. During the time the survey had been carried out, any epidemic of rubella was not reported at the base.
2) In comparison of the positive rates of sera among groups devided by the native prefectures of the donors, Wakayama and Nara prefectural groups showed a little but significantly lower rates than other groups from such urbanized prefectures as Kyoto, Osaka and Hyogo.
3) The serologic conversion of all sero-negative recruits to rubella virus at the enlistment were examined when they were transferred to other bases after accomplishment of 2-month and half training course. From these results, it was clarified that the rubella virus did not perpetuate in such a closed population like a base camp of JGSDF even after a dense epidemic.
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