  The relation between the number of passengers in the main stations and the
infection rate of COVID19 in Tokyo is empirically studied. Our analysis based
on conventional compartment model suggests: 1) Average time from the true day
of infection to the day the infections are reported is about $15$ days. 2) The
scaling relation between the density of active population and the infection
rate suggests that the increase of infection rate is linear to the active
population rather than quadratic, as that is assumed in the conventional SIR
model. 3) Notable deviations from the overall scaling relation seems to
correspond to the change of the peoples's behavior in response to the public
announcements of action regulation.
