Estimating unobserved SARS-CoV-2 infections in the United States

Countries across the world observed dramatic rises in COVID-19 cases and deaths in March 2020. In the United States, delays in the availability of diagnostic testing have prompted questions about the extent of unobserved community transmission. Using a simulation model informed by reported cases and deaths, we estimated that tens of thousands of people (median: ​22,876, 95% posterior predictive interval: 7,451 - 53,044) were infected by the time a national emergency was declared. Our results also indicate that fewer than 10% of locally acquired, symptomatic infections in the US were detected throughout much of late February. These results point to the need for immediate, large-scale efforts to mitigate the impacts of SARS-CoV-2 on the US.