Estimating covid-19 transmission time using hawkes point processes

The question addressed here is whether, using Hawkes models. the distribution of SARS-CoV-2 (Covid-19) transmission times can be estimated accurately with only case-count data. We fit Hawkes models with varying productivities to each of the 50 United States individually, estimating for each state a transmission time density, both nonparametrically and using a normal approximation. We find that, for nearly all states, the estimated transmission times are centered near seven days with a standard deviation of approximately one day. Compared to previous reports, the results here suggest that trans-mission times for SARS-CoV-2 are somewhat shorter, on average, and the distribution is less diffuse, though the results also suggest the possibility of transmission occurring on the first day of exposure.