An epidemiological investigation was carried out on new cases of leprosy between 1906 and 1957 in Aichi Prefecture, mainly in the following leprosaria: Nagashima Aisei-en, Kuryu Rakusen-en, and the Suruga Leprosarium. The findings are as follows.
1. During the 50 years from 1906 to 1957, 1, 546 new cases were found and the incidence rates were between 0.1 and 1.6 per 10, 000 population. The average number of new cases in one year is therefore 29, 7.
2. The prevalence rate was 24.7 per 10, 000 population at the highest, and 5.3 at the lowest. The number of leprosy patients have come to decrease recently.
3. New cases were most frequently observed between the ages of 15 and 19, or 19.7% in rate, and 63.1% of the total cases had begun between the ages of 10 and 29.
4. The disease type L was observed in 59.6%, the type M in 17.0%, and the type N in 23.4%. The type ratio (L/M+N) was 1.47 and has been remarkably improved in the term of Showa (1926-57) in comparison with that in the terms of Meiji (1906-11) and Taisho (1911-1926).
5. The sex ratio was 259.5 during the above mentioned years, and 460.0 in the term of Taisho at the highest, but recently it decreased to 162.2.
6. 42.6% of the total cases had one or more other patients in their own families.
7. In 35.5% of the total cases the symptoms began in Spring; this rate is a little higher than that in other seasons.
8. 75.6% of the total patients or 1, 170 in number, was admitted in leprosaria. In the term of Meiji or Taisho the rate of the patients admitted in leprosaria was lower, but gradual-ly the length of their home residences were shortened. In recent years the patients are admitted in leprosaria immediately after the onset of the disease.
9. In younger patients the period of their home residences were relatively longer, but a comparatively high rate of them were admitted in leprosaria, while the older whose home residences were stabilized, were admitted in leprosaria in lower rate.
10. 7.1% of the total cases were diagnosed to be recovered generally, 45.7% were dead, 24.3% were returned to their own homes. The patients treated in their homes were 1.41 per 10, 000 population at the highest, and 0.41% at the lowest which was recorded recently.
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