The epidemic of influenza in 1983-1984 was mainly caused by Russian A type virus.In it, a peak of occurrence of patients throughout the country was noticed over a period from the end of January to the beginning of February, 1984.Such peak of occurrence of patients, however, was found in Tokyo area in the 50th week of 1983, or over a period from 11 to 17, December.Therefore, there is a large difference in the time of appearance of a peak of epidemic between this area and the whole country.
To interpret the chronological difference in the appearance of such peak, the authors carried out meteorological studies on the epidemic of influenza with the Fukuoka area as a control. The following results were obtained from these studies.
1) Judging from the average atmospheric temperature in the passed years, it was unusually low in both Tokyo and Fukuoka areas in the present epidemic period.There was no significant difference in the average temperature in this period between the two areas.
2) A comparison was made on the number of days (in November and December, 1983) when the average relative humidity was less than 50% between the two areas.As a result, the number was significantly larger in the Tokyo area in these months than in the same area in both months of any other year free from an epidemic of influenza or in the Fukuoka area in the winter of 1983.
3) The number of days in January, February, and March when the average relative humidity exceeded 60% was significantly larger in Tokyo area in the 1983-1984 epidemic period than in any ordinary year.
In conclusion, it was indicated that there was a remarkable relationship between the number of days in November and December, 1983, when the average relative humidity was less than 50% and the chronological difference in the appearance of a peak of prevalence of unfluenza in the 1983-1984 epidemic period between Tokyo area and the whole country.