Whether there was a latent period of COVID-19 development in Saint Petersburg? Mathematical simulation results and facts

The hypothesis of a latent period of development of the first wave of COVID-19 in St. Petersburg is being verified. According to this hypothesis, the appearance of the first patient was preceded by the latent formation of a local variant of the pathogen, caused by the introduction of the pathogen from outside and occurring in a mass of individuals with an asymptomatic course. A mathematical model with two developmental branches, asymptomatic and clinically manifest, was proposed. The possibility of exacerbation of the asymptomatic form or its completion is provided. Other features of the model include: accounting for asymptomatic forms, mild and severe forms of the disease, a decline in population immunity due to the genetic drift of the pathogen. Reception of sequential identification of model in conditions of shortage of data is proposed. It is demonstrated that verification of the mathematical model requires a sufficiently large number of asymptomatic individuals at the time of discovery of the first patient, which is an argument in favor of the validity of the hypothesis.