Science https://doi.org/10.1126/science.aba9757 (2020)

Science https://doi.org/10.1126/science.abb3221 (2020)

The outbreak of SARS-CoV-2, which causes the respiratory disease termed COVID-19, started in Wuhan, China, and is now a pandemic. An understanding of the prevalence and contagiousness of the disease, and of whether the strategies used to contain it to date have been successful, is important for understanding future containment strategies.

One strategy for containment of SARS-CoV-2 is restriction of travel. After 23 January, 2020, long-range travel restrictions in China were imposed by shutting down airports. Chinazzi et al. have used a metapopulation-level disease-transmission model to predict the effects of the travel limitations on the spread of the epidemic. They have found that these measures only modestly affected the epidemic’s trajectory.

Li et al. have used analysis of reported infections within China along with mobility data to infer the epidemiology of SARS-CoV-2. Their analyses indicate that before the travel restrictions, 86% of infections were undocumented. Importantly, undocumented infections were the infection source for 79% of documented cases, thus further indicating that containment will be challenging.