Basing on the epidemiological surveys on the poliomyelitis in the past, Paul assumed that Japan is the area heavily infested by poliomyelitis (polio) virus. Fortunately, a mouse-adapted virus, Lansing strain, was made available by the courtesy of Dr. W. McD. Hammon in 1947. Utilizing this strain of virus, attempts were made to investigate from the angle of neutralization antibody by neutralization tests using mice as to what extent the polio virus is prevailing in Japan. In this case, it is assumed that the most part of the neutralizing substance against Lansing strain is the specific antibody, although the total neutralizing substance existing in the serum against Lansing strain is not necessarily induced by the invasion of that particular virus. Neutralization test employing Lansing strain were performed on 196 normal human sera collected in 1947-4948 in Tokyo, the results of which have been reported. According to those results, the positive rate in the case of sera taken from umbilical cord of newborn is as high as 96%, but the positive rate in 6-12 month age-group is 0% which is the lowest. Thereafter the rate increases in the Niger agegroup. For instance, the rate is 45% in the 8-10 year age-group and 88-100% in the age-group of more than 20. Further, similar investigations were performed on 121 normal human sera collected in Hokkaido and 107 normal human sera collected in Aomori Prefecture. In both cases, it was confirmed that the positive rate is lower compared with the results of the similar tests made on the sera taken in Tokyo. The present investigation was attempted to survey the geographical distribution as well as to what extent the polio virus is prevailing throughout the country by means of the similar tests on the sera collected in various parts of Japan.
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