Summary report on the Asian influenza epidemic in Japan, 1957.

The epidemic of Asian influenza began in Japan in May 1957, reaching a peak towards the end of June, subsiding, and showing a second, equally serious, wave in November-December. The method and place or places of its introduction into the country are not clear, but the important role of schoolchildren in its spread seems well established. While the average attack-rate for the country as a whole was some 26% in the first epidemic wave, it was as high as 50%-60% in concentrated communities such as schools and military camps. The severity of the illness was not very great in the population as a whole, but the death-rates among infants and the aged were remarkably high. The main causes of death were acute pneumonia and cardiac insufficiency. Vaccination of the general population was not carried out on a wide scale.