Estimating the Final Epidemic Size for COVID-19 Outbreak using Improved Epidemiological Models

Final epidemic sizes of different geographical regions due to COVID-19 are estimated using logistic, SIR and generalized SEIR models. These models use different parameters which are estimated using non-linear fits from the available data. It is found that both SIR and generalized SEIR models give similar estimations for regions where curves show signs of flattening. A study of these models with data from China indicates that in such cases these estimates may be more reliable. However, recent trend indicate that unlike China, the decline in infection rate for the US and other European countries is very slow, and does not follow a symmetric normal distribution. Hence a correction is introduced to account for this very slow decline based on the data from Italy. The estimates with all these models are presented for the most affected countries due to COVID-19. According to these models, the final epidemic size in the US, Italy, Spain, and Germany could be 1.1, 0.22, 0.24 and 0.19 million respectively. Also, it is expected that curves for most of the geographical regions will flatten by the middle of May 2020.