  During a long-running pandemic a pathogen can mutate, producing new strains
with different epidemiological parameters. Existing approaches to epidemic
modelling only consider one virus strain. We have developed a modified SEIR
model to simulate multiple virus strains within the same population. As a case
study, we investigate the potential effects of SARS-CoV-2 strain B.1.1.7 on the
city of Moscow. Our analysis indicates a high risk of a new wave of infections
in September-October 2021 with up to 35 000 daily infections at peak. We
open-source our code and data.
