A number of epidemics, including the SARS-CoV-1 epidemic of 2002-2004, have been known to exhibit superspreading, in which a small fraction of infected individuals are responsible for the majority of new infections. The existence of superspreading implies a fat-tailed distribution of infectiousness (new secondary infections caused per day) among different individuals. Here, we present a simple method to estimate the variation in infectiousness by examining the variation in early-time growth rates of new cases among different subpopulations. We use this method to estimate the mean and variance in the infectiousness, k , for SARS-CoV-2 transmission during the early stages of the pandemic within the United States. We find that \sigma _k /\mu _k \gtrsim 3.2, where \mu _k is the mean infectiousness and \sigma _k is its standard deviation, which implies pervasive superspreading. This result allows us to estimate that in the early stages of the pandemic in the USA, nearly 81 %DIFDELCMD < \\%%% %DIF < of new cases were a result of the top 10\\% of most infectious individuals.abstract 
A number of epidemics, including the SARS-CoV-1 epidemic of 2002-2004, have been known to exhibit superspreading, in which a small fraction of infected individuals is responsible for the majority of new infections. The existence of superspreading implies a fat-tailed distribution of infectiousness (new secondary infections caused per day) among different individuals. Here, we present a simple method to estimate the variation in infectiousness by examining the variation in early-time growth rates of new cases among different subpopulations. We use this method to estimate the mean and variance in the infectiousness, \beta , for SARS-CoV-2 transmission during the early stages of the pandemic within the United States. We find that \sigma _\beta /\mu _\beta \gtrsim 3.2, where \mu _\beta is the mean infectiousness and \sigma _\beta its standard deviation, which implies pervasive superspreading. This result allows us to estimate that in the early stages of the pandemic in the USA, over 81 %DIFDELCMD < \\%%% %DIF < of new cases were a result of the top 10\\% of most infectious individuals.abstract \% of new cases were a result of the top 10\% of most infectious individuals.
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