国立競技場の感染リスク「低い」　観客１万人、スパコンで試算―文科省

　文部科学省は６日、東京五輪・パラリンピックの開会式などが開かれる国立競技場での新型コロナウイルスの感染リスクについて、１万人の観客が入った場合を想定しても「リスクは低い」とする試算結果を公表した。
　試算は、文科省の指示を受け、理化学研究所がスーパーコンピューター「富岳」（神戸市）を使って実施。観客１万人の中に従来株の感染者１０人がいると仮定して４時間滞在した場合、新規感染者が何人生じるかを予測した。
　その結果、設計通り毎秒０．７メートルの風が観客席の後方から吹く場合、座席を詰めて座ると新規感染者は０．０８人となった。前後左右に空席を設けるとほぼゼロだった。
　一方、前方から風が吹くと、階段状の座席配置が影響し、後席の観客が飛沫（ひまつ）を浴びやすくなりリスクが増加した。空席なしだと４．７人、１席ずつ空けた場合は０．２３人となった。（2021/07/06-17:19）

The Japan National Stadium, the main venue for this summer's Tokyo Olympics and Paralympics, has a low risk of spreading COVID-19 even with 10,000 spectators, the education ministry said Tuesday.
   The ministry calculated the risk using the Fugaku supercomputer, which estimated how many people would newly test positive for the novel coronavirus if 10 out of the 10,000 spectators were infected with the original strain and stayed at the stadium for four hours.
   The supercomputer found that if wind were to blow from behind the guests' seats at 0.7 meter per second, in line with the stadium design, 0.08 people would be newly infected if they sat without vacant seats in between. If they sat apart, the number would be close to zero.
   The estimated number of newly infected people would increase if the wind came from in front of the spectators, as it would become easier for those at the back to inhale droplets containing the virus due to the seats being arranged in tiers.
   The estimated number came to 4.7 when spectators sat close to each other, while it stood at 0.23 with spectators sitting one seat apart.