Extended Data Fig. 5: Crowding and the temporal clustering of transmission of COVID-19 in Italy.

a, negative association between log10 of epidemic peakedness, as measured by Shannon’s diversity index (Methods), and log population crowding, as measure by Lloyd’s mean crowding (Methods). The point sizes indicate the size of the population in each city, b, Map of epidemic peakedness in Italy at the provincal level. Blue and green colours indicate lower peakedness and red and yellow colours higher peakedness. Grey prefectures had either no or very limited amount of reported cases. Values were rescaled so that Shannon index in each province = (Shannon index—min(Shannon index)/(max(Shannon index)—min(Shannon index)).