[Spanish flu related data]

Abstract

Swine flu epidemic is a current topic, and data relating to Spanish flu pandemic from 1918 to 1920 were presented for your information. Monthly trend of number of deaths due to influenza, acute bronchitis, pneumonia and bronchopneumonia together with PTB, other TB and TB of all forms from 1917 to 1920 was presented in Table 1 and Fig. 1. Flu epidemics in early 1917 and from winter 1917 to spring 1818 were so-called common seasonal flu epidemic, however, new pandemic started from October 1918, and the number of deaths due to flu increased 14 times compared with previous month in October, 19 times in November, and the pandemic reached the summit, and started to decrease from December, however, marked decline was seen only after April 1919. The number of deaths due to flu started to increase again from November 1919, and reached its summit again in January 1920, and the pandemic ended in July. The age- and sex-specific mortality rate due to influenza in 1918 was shown in Fig. 2. The rate was high among infants, 20s and 30s and elderly, and by sex, the rate of female was higher below 35 and lower above 35. The number of deaths due to acute bronchitis and pneumonia and bronchopneumonia fluctuated in parallel with that of influenza, and deaths due to these conditions were very difficult to differentiate, and the impact of flu could better be evaluated by summing up all these three conditions, the sum of deaths due to three conditions was expressed as influenza related death. The proportion of deaths due to three conditions by age group was shown in Fig. 3. The proportion of acute bronchitis was high in infants and elderly, and in the other age groups, influenza occupied around 30% and pneumonia and bronchopneumonia around 70% of influenza related death. Total number of deaths due to influenza related diseases from 1918 to 1920 was 816,884, and the annual rate was 489.4 per 100,000. Annual age- and sex-specific mortality rate due to influenza related diseases was shown in Fig. 4, and it showed similar pattern with that of influenza. Because of huge excess death of TB patients due to influenza and related diseases, TB mortality in Japan, which had been increasing since 1884, started to decrease since 1919, and TB mortality which had been decreasing slowly since the beginning of 20th century in European countries and the US, the decline was accelerated since 1919.