抄録
An epidemic of Russian type A influenza was prevalent in Japan during the 1983-1984 period. When the weekly incidence of this disease in Tokyo was compared to that of the whole country, a remarkable chronological difference was seen epidemiologically. To interpret the chronological difference in the occurrence of the epidemic, meteorological conditions were examined in the Tokyo, Hokkaido, Osaka, Shimane and Fukuoka districts. The following results were obtained:
1) Over a period from November, 1983 to March, 1984, there were more days when the average atmospheric temperature was lower than that in an average year. The rate of those days over this period to those in an average year was about 60% in the Hokkaido district, about 80% in the Tokyo, Osaka, and Shimane districts, and 73% in the Fukuoka district. Therefore, usually low temperatures were prevalent all over the country during this period, which is an epidemic season of influenza. There were no large differences in that rate among the five districts.
2) In the early stage of this period (November to December, 1983), the number of days when the average relative humidity was less than 50% was significantly larger in the Tokyo district than in any other district. It was also significantly larger in the Tokyo district in that stage than in the same stage of an average year. On the contrary, the number of days when the average relative humidity was more than 60% was significantly smaller in the Tokyo district than in any other district. It was also significantly smaller in the Tokyo district in that stage than in the same stage of an average year.
3) In the late stage of the period examined (January to March, 1984), the number of days when the average relative humidity was more than 60% was significantly smaller in the Hokkaido, Shimane, and Fukuoka districts than that in the same stage, or January to March, of an average year. On the other hand, it was significantly larger in the Tokyo district in these months of 1984 than in the same month of an average year.
In conclusion, the chronological difference in the occurrence of an influenza epidemic in the Tokyo district over the period from November, 1983 to March, 1984, could be interpreted meteorologically. That is, it was brought about by the fact that there were a large number of days in this district in November and December, 1983, when the average relative humidity was less than 50%, and a small number of days in the same district in the same period when the average relative humidity was more than 60%.
