Modeling SARS-CoV-2 in mice: Among the research tools necessary to develop medical interventions to treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, high on the list are informative animal models with which to study viral pathogenesis. Gu et al. developed a mouse model in which a SARS-CoV-2 strain was infectious and could cause an inflammatory response and moderate pneumonia. Adaptation of this viral strain in the mouse appeared to be dependent on a critical amino acid change, Asn ⁵⁰¹ to Tyr (N501Y), within the receptor-binding domain of the viral spike protein. The new mouse model was used to study neutralizing antibodies and a vaccine candidate against the virus. Science , this issue p. 1603

With the emergence of highly infectious variants of the SARS-CoV-2 virus, Covid-19 inevitably started to spread in Chinese megacities, where the government used to take adequate measures to suppress the increase of Covid-19 cases since 2020. For instance, in the spring of 2022, Shanghai, a megacity with a population of 30 million, was locked down for two months to restrain the outbreak of Covid-19. In the megacities’ long- term lockdown, fresh food supply tends to be crucial, especially when residents cannot store sufficient fresh vegetables without going out for more than a month. In this case, as an emerging business model, the fresh food e-commerce platforms become residents’ primary source of fresh food supply during the lockdown. The operating strategy of the fresh food e-commerce platforms is of great significance for assisting the government in stabling residents’ moods and realizing the dynamic zero policy, which would also be helpful to their penetration. However, the strict quarantine policy of the government reduces the number of delivery riders resulting in soaring prices, which will influence residents’ decisions of whether to bear economic losses of high prices or physical damages due to lack of food. This paper analyzes the strategic choices between the government, fresh food e-commerce platforms, and residents (consumers) through the evolutionary game model, which provides solid suggestions for possible lockdowns in other Chinese megacities against Covid-19.