Incubation period of COVID-19 in the “live-house” cluster of accurately known infection events and delay time from symptom onset of public reporting observed in cases in Osaka, Japan

The incubation period of an infectious disease is very important for control of the disease but estimating the period is not easy because the date of infection is not easy to identify. Accurate incubation period distribution by examining cases in the cluster generated in “live-houses” in Osaka, Japan with known infection events is reported. The distribution of the latent period is also estimated. The modes of incubation and latent periods of COVID-19 in Japan are 4.1 days and 3.3 days, respectively. The mode of the delay time from the onset to reporting is estimated to be 4.7 days, telling that the effects of interventions show up in the number of infections two weeks later after the measures.