This just came out in Science, one of the world's two most elite scientific journals. Authors are from several countries (London, NYC, Beijing, Davis CA, Hong King). It shows the biggest challenge controlling this virus. Basically the vast majority of spread is from people with few or no symptoms. it’s hard to get people who feel fine to stop engaging with other people, who also feel fine.
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Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2)
Ruiyun Li1,*, Sen Pei2,*,†, Bin Chen3,*, Yimeng Song4, Tao Zhang5, Wan Yang6, Jeffrey Shaman2,†
Science 16 Mar 2020:
eabb3221
DOI: 10.1126/science.abb3221
Abstract
Estimation of the prevalence and contagiousness of undocumented novel coronavirus (SARS-CoV2) infections is critical for understanding the overall prevalence and pandemic potential of this disease. Here we use observations of reported infection within China, in conjunction with mobility data, a networked dynamic metapopulation model and Bayesian inference, to infer critical epidemiological characteristics associated with SARS-CoV2, including the fraction of undocumented infections and their contagiousness. We estimate 86% of all infections were undocumented (95% CI: [82%–90%]) prior to 23 January 2020 travel restrictions. Per person, the transmission rate of undocumented infections was 55% of documented infections ([46%–62%]), yet, due to their greater numbers, undocumented infections were the infection source for 79% of documented cases. These findings explain the rapid geographic spread of SARS-CoV2 and indicate containment of this virus will be particularly challenging.