Covid-19 is firstly reported in Dec 2019 and has spread to countries around the world. Variants represented by alpha, beta, gamma, delta, and omicron strains have been reported as of Jul 2022 and the pandemic has not yet ended.
It is reported that the number of Covid-19 cases and deaths differ among regions and countries, and the virus mutation, measures to prevent the spread of infection such as lockdown, social distance strategy, therapeutic drugs and vaccination, or other factors such as population or economic activities can cause the difference. However, it is difficult to quantitatively evaluate the effect of each factor on increase or decrease of the cases and deaths when the data from a country is analyzed since various factors are complicatedly related and change with time.
In this study, we described the dynamics of infectious diseases using a mathematical model based on SIR model, performed population analysis on the number of Covid-19 cases, confirmed deaths and excess deaths from over 150 countries using MCMC method, and examined the factors which can explain the difference of the cases and deaths by regions and countries. The effect of lockdown could be described with the model in which the potential of lockdown decreases with time, and the difference of transmissibility among variants could be estimated successfully.