Development of the Covid-19 Epidemic Model: Calculations for a Mutating Virus

Abstract

Our previously developed simple analytical model for calculating the epidemic spread of COVID 19 is further developed. We propose a calculation method for analyzing the spread of the two-strain virus system. Comparison of the calculation results with statistical data on the example of the United Kingdom, the United States and South Africa shows their satisfactory agreement. A methodology for calculating epidemic growth under conditions of abrupt changes in lockdown conditions is proposed. It is shown that both empirical coefficients included in the model can be calculated on the basis of information on population size and quarantine conditions during the epidemic. Preliminary recommendations for determining these coefficients are given. Reliable calculation of the model coefficients will make it possible to transform the proposed calculation methodology into a higher class of models for operational and long-term forecasting of epidemic spread depending on the conditions determining this process. A method for calculating epidemic growth under conditions of simultaneous action of several virus strains is proposed. Comparison of calculation results on proposed ratios for countries with intensive recurrent epidemic growth due to virus mutation is in satisfactory agreement with statistical data. The method of calculation of epidemic growth under sharp changes of lockdown conditions is developed. To confirm the possibility of using this method it is necessary to compare the results of calculations with the data of statistics. When the results of the calculations are compared with statistical data, a systematic bias is observed from late February and early March onwards. For countries where vaccination is intensively carried out, this deviation can be explained by a decrease in the proportion of the population that can be infected by contact with infected persons. However, such differences for South Africa, where intensive vaccination is not carried out, require further investigation.