Using ILI surveillance to estimate state-specific case detection rates and forecast SARS-CoV-2 spread in the United States

Justin D Silverman; Alex D Washburne

The true prevalence of SARS-CoV-2 is unknown. However, if we assume the excess non-influenza ILI is almost entirely due to SARS-CoV-2, an assumption that becomes more valid as the virus becomes more prevalent, we can use the excess non-influenza ILI to define bounds and understand 110 the mutual dependence of exponential growth rates, the rate of subclinical infections, and the time between the onset of infectiousness and a patient reporting as ILI Figure 3 . With a January 15 start date of the US epidemic [10] , allowing early stochasticity from start-time to the onset of regular exponential growth, we find that it's impossible to explain the ILI surge with an epidemic whose doubling time is longer than 3.5-days, as such slow growth scenarios fail to produce enough 115 infected individuals to match the observed excess ILI.