"低濃度感染假說"有意思。
學校的報告:
Date Number of positive students
2021/01/21 1
2021/01/18 1
2021/01/15 2
2021/01/14 1
2021/01/13 2
2021/01/11 2
2021/01/08 1
2021/01/07 2
2021/01/02 10