Figure 5
Time evolution of the effective reproduction numbers. Moving averages of the effective reproduction number for the entire city, \(Re^{city}\) (blue \(\circ\)), for buses, \(Re^{bus}\) (gray \(\times\)), and for healthcare workers in the buses, \(Re^{health}\) (red \(+\)). We find that \(Re^{bus}\) consistently follows \(Re^{city}\) during the local COVID-19 outbreak, except for a three-month period between the first and the second waves of daily cases. We also show that \(Re^{health}\) was systematically higher than \(Re^{bus}\), which unveils that the healthcare workers played an important role in the transmission within buses during the first wave of COVID-19 in Fortaleza. The inset shows that the maximum ratio \(Re^{health}/Re^{bus}\) occurred soon after the lockdown period. The windows of moving averages have 22 days of width with step size of 5 days for all curves. In the period indicated by the shaded regions in the main plot and its inset, both \(Re^{bus}\) and \(Re^{health}\) decayed to undetectable standards, i.e., no CCs could be identified under the framework of our contact tracing approach. The vertical dotted lines represent the beginning of social isolation (State Decree 33,519), lockdown (State Decree 33,574), and economic reopening (State Decree 33,608) regimes imposed on March 20, May 8, and June 1, 2020, respectively. We also highlight, in light red, the lockdown period in the city of Fortaleza.
