Crowding and the epidemic intensity of COVID-19 transmission

Benjamin Rader; Samuel Scarpino; Anjalika Nande; Alison Hill; Benjamin Dalziel; Robert Reiner; David Pigott; Bernardo Gutierrez; Munik Shrestha; John Brownstein; Marcia Castro; Huaiyu Tian; Bryan Grenfell; Oliver Pybus; Jessica Metcalf; Moritz U.G. Kraemer

is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.04.15.20064980 doi: medRxiv preprint performed a simple linear regression. We found that peak incidence was correlated with epidemic 140 intensity (locations that had high intensity also had more cases at the peak). Total incidence, however, 141 was larger in areas with lower estimated intensity, which is intuitive as crowded areas have longer 142 epidemics that affect more people (Extended Data Table 2 ). This suggests that measures taken to 143 mitigate the epidemic may need to be enforced more strictly in smaller cities to lower the peak incidence 144 (flatten the curve) but conversely may not need to be implemented as long. Furthermore, with lower total 145 incidence in small cities, the risk of resurgence may be elevated due to lower population immunity. There 146 is urgent need to collect serological evidence to provide a full picture of attack rates across the world 26 . 147 148 Using our model trained on cities in China we extrapolated epidemic intensity to cities across the world 149 (Figure 3) . Figure 3 shows the distribution of epidemic intensity in 380 urban centers. Cities in yellow 150 are predicted to have higher epidemic intensity relative to those in blue (a full list is provided in 151 Extended Data Table 3 ). Small inland cities in sub-Saharan Africa had high predicted epidemic intensity 152 and may be particularly prone to experience large surge capacity in the public health system 27 . In general, 153 coastal cities had lower predicted intensity and larger and more prolonged predicted epidemics. Global 154 predictions of epidemic intensity in cities rely on fitted relationships of the first epidemic curve from 155